Glossary of Watch Terms
Navigate your way through all the horological jargon with our handy glossary
Navigate your way through all the horological jargon with our handy glossary
An acrylic crystal composed of plastic composite that is generally less expensive than a glass or mineral crystal. Sometimes called an “unbreakable” crystal, though this is a misnomer as they can definitely break. A high-quality acrylic crystal has optical properties very similar to glass.
Derived from Latin ad justus, meaning just right. Adjusted to compensate for temperature, positions, and isochronism.
AGE OF THE MOON
The time that has elapsed since the new moon. In some watches, the 29 1/2 days of the lunar month are indicated on a lunar dial.
A watch provided with a movement capable of releasing an acoustic sound at the time set. A second crown is dedicated to the winding, setting and release of the striking-work; an additional center hand indicates the time set. The section of the movement dedicated to the alarm device is made up by a series of wheels linked with the barrel, an escapement and a hammer striking a gong or bell. Works much like a normal alarm clock.
ALL OR NOTHING PIECE
A repeating watch mechanism which insures that all the hour and minutes are struck or sounded or nothing is heard.
A device that determines altitude by responding to changes in barometric pressure.
Maximum angle by which a balance or pendulum swings from its rest position.
A display that shows the time with hour and minute hands (an analog display) as well as digital numbers (a digital display).
ANALOG OR ANALOGUE
A watch displaying time indications by means of hands.
Heating and cooling a metal slowly to relieve internal stress.
The automatic allowances for the different lengths of each month of a year in the calendar module of a watch. This type of watch also usually shows the date and month, and most of the time the phases of the moon.
Said of a watch whose movement is not influenced by electromagnetic fields that could cause two or more windings of the balance spring to stick to each other, consequently accelerating the rate of the watch. This effect is obtained by adopting metal alloys (e.g. Nivarox) resisting magnetization.
Superficial glass treatment assuring the dispersion of reflected light. Better results are obtained if both sides are treated, but in order to avoid scratches on the upper layer, the treatment of the inner surface is preferred. A film created by steaming the crystal to eliminate light reflection and to improve legibility. Anti reflection functions best when applied to both sides of the crystal, but because it scratches, some producers prefer to have it only on the interior of the crystal. It is mainly used on synthetic sapphire crystals.
Small opening. The dials of some watches (in French: montres a guichet) have apertures in which certain indications are given (the date, hour, etc.)
The process of cutting pieces of one material and applying them to the surface of another material. (Hour markers on a watch dial often have Arabic numerals, Roman numerals and other marker symbols applied in this fashion.)
1, 2, 3, 4, 5, 6, 7, 8, 9, 0
Bearing element of a gear or balance, whose ends – called pivots – run in jewel holes or brass bushings.
The mechanical axle of a moving part; on the balance it is called the staff, on the lever it is called the arbor.
A style of design that was popular in the 1920s and 1930s (and has a lasting impact on jewelry, architecture and other arts in current times) marked by stylized forms and geometric designs, bold colors, and the use of plastic and glass that was adapted to mass production.
A style of decoration and architecture of the late 19th and early 20th centuries, characterized particularly by the depiction of leaves and flowers in flowing designs, and by many curves or turns and winding designs.
Analyzing a metal for its gold or silver content.
Process of fitting together the components of a movement. This was formerly done entirely by hand, but the operations have now been largely automated. Nevertheless, the human element is still vital, especially for nspection and testing.
Graduations on the dial of a chronograph for measuring the respiration rate.
Irregular in shape or outline; “asymmetrical features”; “example: a dress with an crooked hemline.”
ATOMIC TIME STANDARD
Provided by the U.S. National Institute of Standards and Technology, Time and Frequency Division, Boulder, Colorado. Atomic time is measured through vibrations of atoms in a metal isotope. The result is extremely accurate time that can be measured on instruments. A radio signal transmits this exact time throughout North America and some ‘atomic’ watches and clocks can receive them and correct to the exact time.
Unit of pressure used in watch making to indicate water-resistance.
AUTO REPEAT COUNTDOWN TIMER
A countdown timer that resets itself as soon as the preset time has elapsed, and starts the countdown again. It repeats the countdown continuously until the wearer pushes the stop button.
A watch whose mechanical movement is wound automatically. A rotor makes short oscillations due to the movements of the wrist. Through a series of gears, oscillations transmit motion to the barrel, thus winding the mainspring progressively.
A rotating weight, set into motion by moving the wrist, winds the going barrel via the gear train of a mechanical watch movement. Automatic winding was invented during the pocket watch era in 1770 by Abraham-louis Perrelet, who created a watch with a weight swinging to and fro (when carried in a vest pocket, a pocket watch usually makes vertical movements). The first automatic-winding wristwatches, invented by John Harwood in the 1920s, utilized so-called hammer winding, whereby a weight swung in an arc between two banking pins. The breakthrough automatic winding movement via rotor began with the ball bearing Eterna-Matic in the late 1940s, and the workings of such a watch haven’t changed fundamentally since. Today we speak of unidirectional winding and bi-directionally winding rotors, depending on the type of gear train used.
Automatic working figures moving in conjunction with the movement mechanism. Striking Jacquemarts or jacks which are figures (may be humans provided with hammers) striking bells to supply the sound for the hour and quarter hours. The hammers take the place of the bells clapper. Automata is the plural of automation.
For middle temperature errors found on marine chronometers.
Any extra dial for information (dates, days, months, timers etc.)
American Watchmakers-Clockmakers Institute. (701 Enterprise Drive, Harrison, OH 45030 – Telephone: 513-367-9800)
A French term for an oblong shape. A watch having it’s length at least 3 times it’s width. A long narrow diamond.
Oscillating device that, together with the balance spring makes up the movement’s heart inasmuch as its oscillations determine the frequency of its functioning and precision.
The heart of a mechanical watch movement is the balance. Fed by the energy of the mainspring, a tirelessly oscillating little wheel, just a few millimeters in diameter and possessing a spiral-shaped balance spring, sets the rhythm for the escape wheel and lever with its vibration frequency. Today the balance is usually made of one piece of anti-magnetic glucydur, which expands very little when exposed to heat.
The bridge that holds the upper jewels and the balance and secured at the end only.
Component of the regulating organ that, together with the balance, determines the movement’s precision. The material used is mostly steel alloy (e.g. Nivarox), an extremely stable metal compound. In order to prevent the system’s center of gravity from continuous shifts, hence differences in rate due to the watch’s position, some modifications were adopted. These modifications included Breguet’s overcoil (closing the terminal part of the spring partly on itself, so as to assure an almost perfect centering) and Philips curve (helping to eliminate the lateral pressure of the balance-staff pivots.
The shaft of the balance wheel.
The part of a mechanical watch movement that oscillates, dividing time into equal segments.
The two pins which limit the angular motion of the pallet.
A type of movement employing about six bridges to hold teh train. This movement was being used by 1840.
Component of the movement containing the mainspring, whose toothed rim meshes with the pinion of the first gear of the train. Due to the fact that the whole – made up of barrel and mainspring – transmits the motive force, it is also considered to be the very motor. Inside the barrel, the mainspring is wound around an arbor turned by the winding crown or in the case of automatic movements, also by the gear powered by the rotor.
Any non-precious metal such as steel.
BATTERY RESERVE INDICATOR
A feature of a battery-powered watch that shows how much longer the watch will operate before the battery should be replaced.
Part on which a pivot turns, in watches mostly a jewels.
Refers to the tick or sound of a watch; about 1/5 of a second. The sound is produced by the escape wheel striking the pallets.
An hour hand resembling a stag beetle; usually associated with the poker-type minute hand in 17th and 18th century watches.
Four parts copper and one part tin used for metal laps to get a high polish on steel.
Chamfering of edges of levers, bridges and other elements of a movement by 45?, a treatment typically found in high-grade movements.
Top part of case, sometimes holds the crystal. It may be integrated with the case middle or a separate element. It is snapped or screwed on to the middle.
BI-DIRECTIONAL ROTATING BEZEL
A bezel that can be moved either clockwise or counterclockwise. These are used for mathematical calculations or for keeping track of elapsed time.
A balance composed of brass an steel designed to compensate for temperature changes in the hairspring.
BLIND MAN’S WATCH
A Braille watch; also known as a tact watch.
Traditionally, high quality movements were fitted with screws which were artificially blued, more for decoration than function.
BLUING (OR BUING)
If polished steel is heated to 540 degrees, the color will change to blue.
Convex on one side.
The ring that is looped at the pendant to which a chain or fob is attached.
A marine or other type chronometer in gimbals so the movement remains level at sea.
BOX JOINTED CASE
A heavy hinged decorative case with a simulated joint at the top under the pendant. (Also called the Box Case.)
A metal band attached to the case. It is called integral if there is no apparent discontinuity between case and bracelet and the profile of attachments is similar to the first link.
A particular type of hands in a traditional elegant shape.
A ratcheting watch key permitting winding in only one direction.
A type of hairspring that improves time keeping also called over-coil hairspring.
Structural metal element of a movement – sometimes called cock or bar – supporting the wheel train, balance, escapement and barrel. Each bridge is fastened to the plate by means of screws and locked in a specific position by pins. In high quality movements the sight surface is finished with various types of decoration.
Topical finishing giving metals a line finish, a clean and uniform look.
A Rolex watch which were water proof (Oyster) and auto wind (Perpetual) circa 1930 to the 1950s.
The fastening for a strap, consisting of a rim and tongue. It attaches the two parts of the leather strap around the wrist.
Buffer spring is a stop spring for oscillating weight.
BULL’S EYE CRYSTAL
Used on old type watches; the center of the crystal was polished which achieved the bull’s eye effect.
A “bumper watch” is a watch with an automatic movement. Instead of having a full rotor (360 degrees of rotation) it has what is sometimes referred to as a hammer rotor, and this hammer rotor swings back and forth inside the case approximately 300 degrees striking a small spring mounted to a platform at each side. When the hammer rotor hits this spring it is propelled back the other way until it strikes the spring at the other side [or end] of the platform and so on. The sound it makes is a kind of “clang” or “bump” thus the name “bumper watch.”
Any kind of precious stone, such as sapphire, ruby or emerald, uncut and only polished, generally of a half-spherical shape, mainly used as an ornament of the winding crown or certain elements of the case.
An intermediate complication between a simple calendar and a perpetual calendar. This feature displays all the months with 30 or 31 days correctly, but needs a manual correction at the end of February. Generally, date, day of the week and month, or only day and month are displayed on the dial.
With respect to the Julian Calendar, the calendar reform introduced by Pope Gregory XIII in 1582 corrected the slight error of the former calendar by suppressing a leap year numbers are divisible by 400 (this entailed the elimination of the leap years in 1700, 1800 and 1900, but not in 2000 and 2400). In non-Catholic countries this reform was introduced after 1700.
Displaying date, day of the week and month on the dial, but needing a manual correction at the end of a month with less than 31 days. It is often combined with the moon phase.
The calendar established by Julius Caesar was based on the year duration of 365.25 days with a leap year with 366 days every 4 years. In 325 AD, this calendar was adopted by the Church. Due to the slight error (0.0078 day) implied in this time count, the Julian Calendar was later replaced by the Gregorian Calendar.
This is the most complex horology complication related to the calendar feature, as it indicates the date, day, month and leap year and does not need manual corrections until the year 2100 (when the leap year will be ignored).
Originally it indicated only the size (in lines, “‘) of a movement, but now this indication defines a specific movement type and combines it with the constructor’s name and identification number. Therefore the caliber identifies the movement.
Often used to refer to a curved or arched dial or bezel.
An element in the shape of a hollow cylinder, sometimes also called pipe or bush, for instance the pipe of the hour wheel bearing the hour hand.
Also called the end stone, the flat jewel on which the staff rests.
Device similar to the tourbillon, but with the carriage not driven by the fourth wheel, but by the third wheel.
CARRIAGE OR TOURBILLON CARRIAGE
Rotating frame of a tourbillon device, carrying the balance and escapement. This structural element is essential for a perfect balance of the whole system and its stability, in spite of its reduced weight. As today’s tourbillon carriages make a rotation per minute, errors of rate in the vertical position are eliminated. Because of the wide spread use of transparent dials, carriages became elements of aesthetic attractiveness.
The metal housing of a watch’s parts. Stainless steel is the most typical metal used but titanium, gold, silver, and platinum are also used. Less expensive watches are usually made of brass and plated with gold or silver.
A screw with part of its head cut away.
The second wheel; the arbor for the minute hand; this wheel makes one revolution per hour.
Looks like a miniature bi-cycle chain connecting the barrel and fusee.
Sloping or beveled. Removing a sharp edge or edges of holes.
An area hollowed out and filled with enamel and then baked on. Hand-made treatment of the dial or case surface. The pattern is obtained by hollowing a metal sheet with a graver and subsequently filling the hollows with enamel.
The hour, minute and seconds numbers on a dial. The chapter ring is the zone or circle that confines the numbers.
Hour-circle, i.e. the hour numerals arranged on a dial.
The bell-like sound made when a clock strikes on the hour, half-hour, etc. Two familiar chimes traditionally found in clocks are the Westminster chime made by the famous Big Ben in London, and the bim-bam, a two-note chime. Striking-work equipped with a set of bells that may be capable of playing a complete melody. A watch provided with such a feature is called chiming watch.
A watch that includes a built-in stopwatch function, i.e. a timer that can be started and stopped to time an event. There are many variations of the chronograph. From the Greek chronos (time) and graphein (to write). Originally a chronograph literally wrote, inscribing the time elapsed on a piece of paper with the help of a pencil attached to a type of hand. Today this term is used for watches that show not only the time of day, but also certain time intervals via independent hands that may be started or stopped at will. So-called stopwatches differ from chronographs because they do not show the time of day. Not be mistaken for a chronometer.
A high-precision watch. According to the Swiss law, a manufacture may put the word “chronometer” on a model only after each individual piece has passed a series of tests and obtained a running bulletin and a chronometer certificate by an acknowledged Swiss control authority, such as the COSC. Literally, “measurer of time.” As the term is used today, a chronometer denotes an especially accurate watch (one with a deviation of no more than five seconds a day for mechanical movements). Chronometers are usually supplied with an official certificate from an independent office such as the C.O.S.C.
A detent escapement used on marine chronometers.
Superficial decoration applied to bridges, rotors and pillar-plates in the shape of numerous slightly superposed small grains, obtained by using a plain cutter and abrasives. Also called Pearlage or Pearling.
The fastening mechanism for bracelet watches. There are many types of clasps.
Deployment Buckle—A three-folding enclosure, which secures the two ends of the bracelet and allows enough room for placing the watch on the wrist when fully deployed. When closed, the buckle covers the two-piece folding mechanism.
Fold-Over Buckle—See Deployment buckle
Hook Lock—Two separate units each fitting on either end of the bracelet which allows the watch to be laid out. One end of the closure hooks onto the other to secure the two ends of the bracelet.
Jeweller’s Clasp—A closure that is generally used on better bracelets. Also allows it to lie flat.
Sliding Clasp—Also a hook type method but allows for easy sizing of the bracelet by sliding up.
Twist Lock—A closure similar to Jeweller’s Clasp used on ladies jewellery bracelets.
A pawl that ratchets and permits the winding wheel to move in one direction; a clicking sound can be heard as the watch is wound.A Pawl isa pivoted tongue or sliding bolt on one part of a machine that is adapted to fall into notches or interdental spaces on another part so as to permit motion in only one direction.
A watch that strikes the hour but not on demand.
A kind of enamel work— mainly used for the decoration of dials—in which the outlines of the drawing are formed by thin metal wires. The colored enamel fills the hollows formed in this way. After oven firing, the surface is smoothed until the gold threads appear again.
CLOUS DE PARIS
Decoration of metal parts characterized by numerous small pyramids.
Some escape wheels have a special design which increases te impulse plane; located at the tip of the tooth of the escape tooth.
16,000 beats per hour.
The metal bar which carries the bearing for the balance’s upper pivot an is supported at one end.
An alloy of 90% fine silver and 10% copper. It is called coin silver because early US coins were a ready source of this raw material and were sometimes melted down and made into watch cases.
Part of chronograph movements, governing the functions of various levers and parts of the chronograph operation, in the shape of a small-toothed steel cylinder. It is controlled by pushers through levers that hold and release it. It is a very precise and usually preferred type of chronograph operation.
A balance wheel designed to correct for temperature.
Additional function with respect to the manual-winding basic movement for the display of hours, minutes and seconds. Today, certain features, such as automatic winding or date, are taken for granted, although they should be defined as complications. The main complications are moonphase, power reserve, GMT, and full calendar. Further functions are performed by the so-called great complications, such as split-second chronograph, perpetual calendar, tourbilon device, and minute repeater.
A wheel with its teeth at a right angle to plane of the wheel.
Movements made by Elgin (and some other firms) that was a means of converting from a hunting case to an open-faced watch or vice-versa.
An artificial leather created and made by DuPont from 1964 to 1971. Many wristwatch bands were made from this material.
Pusher positioned on the case side that is normally actuated by a special tool for the quick setting of different indications, such as date, GMT, full or perpetual calendar.
Abbreviation of “Controle Officiel Suisse des Chronomètres,” the most important Swiss institution responsible for the functioning and precision tests of movements of chronometers. Tests are performed on each individual watch at different temperatures and in different positions before a functioning bulletin and a chronometer certificate are issued, for which a maximum gap of -4/+4 seconds per day is tolerated.
As with a Chronograph, except that the Tachymeter function is found on the watches bezel.
Decoration of rotors and bridges of movements, whose pattern consists of a series of concentric ribs.
COTES DE GENEVE
Decoration applied mainly to high-quality movements, appearing as a series of parallel ribs, realized by repeated cuts of a cutter leaving thin stripes. Also called vogues de Geneve. Surface decoration comprising an even pattern of parallel stripes, applied with a quickly rotating plastic or wooden peg.
Additional hand on a chronograph, indicating the time elapsed since the beginning of the measuring. On modern watches the second counter is placed at the center, while minute and hour counters have off-center hands in special zones, also called subdials.
A function that lets the wearer keep track of how much of a pre-set period of time has elapsed. Some countdown timers sound a warning signal a few seconds before time runs out — these are useful in events such as yacht races, where a sailor must maneuver a boat into position before the start of a race.
A minute crack in the glaze of enamel watch dials.
Usually positioned on the case middle and allows winding, hand setting and often date or GMT hand setting. As it is linked to the movement through the winding stem passing through a hole in the case. For waterproofing purposes, simple gaskets are used in water-resistant watches, while diving watches adopt screwing systems (screw-down crowns).
Wheel meshing with the winding pinion and with the ratchet wheel on the barrel-arbor.
The transparent cover on the watch face made of glass crystal, synthetic sapphire or plastic.
The two pins that change the rate of a watch; the two pins, in effect, change the length of the hairspring.
The inter-dust cover of a pocket watch.
A type of escapement used on some watches.The inter-dust cover of a pocket watch.
The art of producing a design, pattern, or wavy appearance on a metal. American idiom or terminology used in all American factory ads. The European terminology was Fausse Cotes or Geneva Stripes.
A colored or shaded band on a world time clock that shows which time zones are in daylight and which in darkness.
A large-sized ship’s chronometer.
A hunting case with the center designed to allow the position of the hands to be seen without opening the case.
Aaron Dennison was one of the “Fathers” of the American watch industry, and he invented several standards of measuring watches and mainsprings. The Dennison Gauge for watch sizes is based on a size A being 1″ and for each additional size larger, you would add 1/16″. The most common sizes were N (1 11/16), which is close to 18s and L (1 10/16), which is close to 16s. Used primarily by the E. Howard Watch Company (of which Dennison was a founder). Dennison Gauge is still used for the measurement of mainsprings for American pocket watches.
A clasp that folds under the strap of the watch.
An alarm on a diver’s watch that sounds when the wearer exceeds a pre-set depth. In most watches it stops sounding when the diver ascends above that depth.
A detached escapement. The balance is impulsed in one direction; used on watches to provide greater accuracy. Detent a locking device.
A progressive natural change of a watch’s rate with respect to objective time. In case of a watch’s faster rate, the deviation is defined positive, in the opposite case negative.
Face of a watch, on which time and further functions are displayed by markers, hands, discs or through windows. Normally it is made of a brass—sometimes silver or gold.
Said of watches whose indications are displayed mostly inside an aperture or window on the dial.
The geographical direction can be displayed by rotating a bezel or digital readout on the face of the watch using the location of the sun.
DISCHARGE FALLET JEWEL
The left jewel.
Rotary watches marked ‘Dolphin Standard’ on the case back have been upgraded to offer this exclusive waterproof specification meaning that you and your watch can swim and dive all day. Dolphin Standard watches are suitable for: Swimming, shallow diving, yachting, all water sports (excluding scuba diving) and showering.
A watch with one impulse roller table and a safety roller, thus two rollers.
The angular position of the pallet jewels in the pallet frame which causes those jewels to be drawn deeper into the escape wheel under pressure of the escape wheel’s tooth on the locking surface.
Drivers watches were designed to be worn on the side of the wrist while driving a car so that the driver would not have to move the wrist to see the time.
The space between a tooth of the escape wheel and the pallet from which it has just escaped.
A watch that measures current local time as well as at least one other time zone. The additional time element may come from a twin dial, extra hand, subdials, or other means.
A repeating watch with hammers that strikes a block instead of bells or gongs.
An escape wheel with two sets of teeth, one for locking and one for impulse.
Any kind of precious stone, such as sapphire, ruby or emerald, uncut and only polished, generally of a half-spherical shape, mainly used as an ornament of the winding crown or certain elements of the case.
Not exactly circular, non-concentric. A cam with a lobe or egg shape.
A quartz watch that uses a Solar conversion panel and energy cell to provide the operating power. The ability of an Eco-Drive to use light from any source to generate electrical power means that the supply is limitless and free and never needs a battery.
The glass acts as the light energy cell. Located on the top of the glass are very fine strips of amorphous silicon virtually invisible to the naked eye. Electricity is generated as soon as light strikes the glass from the outside and again as it reflects back off the dial. Vitro’ runs for approximately six months once fully charged.
These watches run for approximately 5 years once fully charged (Ladies model 2 years), and feature a perpetual calendar accurate to February 2100. When this watch has not been exposed to light for a certain length of time, the functions begin to shut down. This saves power and extends operating time. In the mean time, the movement’s integrated circuit keeps track of the current time and date. When the watch is once more exposed to light, the hands and date immediately resume their correct positions.
End of Life. In quartz movement watches, the battery should be changed when the seconds hand which starts to jump every four seconds.
End of Energy. System used with the AHP alerts the wearer of accumulator discharge by causing the seconds hand to jump every four seconds instead of every second. The accumulator can then be recharged by turning the crown.
ELAPSED TIME ROTATING BEZEL
A graduated rotating bezel used to keep track of periods of time. The bezel can be turned so the wearer can align the zero on the bezel with the watch’s second or minute hands. The wearer can then read the elapsed time off the bezel. This prevents the wearer from having to perform the subtraction that would be necessary if the watch’s regular dial was used.
Un-drilled jewel, placed on the balance jewel with the tip of the balance-staff pivot resting against its flat surface, to reduce pivot friction. Sometimes used also for pallet staffs and escape wheels.
Decorative engraving, usually on the watch case.
Newer type watch using quartz and electronics to produce a high degree of accuracy.
A hairspring composed of a special alloy of nickel, steel, chromium, manganese and tungsten that does not vary at different temperatures. Elinvar was derived from the words elasticity invariable.
The up and down play of an arbor between the plates and bridge or between the jewels.
The time calculated for the Earth to orbit around the sun.
The time when day and night are of equal length, when the sun is on the plane of the equator. Such times occur twice in a year: the vernal equinox on March 2lst-22nd and the autumnal equinox on September 22nd-23rd.
EQUATION OF TIME
Indication of the difference, expressed in minutes, between conventional mean time and real solar time. This difference varies from -16 to +16 seconds between one day and the other.
The last wheel in a going train; works with the fork or lever and escapes one pulse at a time.
Positioned between the train and the balance wheel and governing the rotation speed of the wheel-train wheels. In today’s horology the most widespread escapement type is the lever escapement. In the past, numerous types of escapements were realized, such as: verge, cylinder, pin pallet, detent and duplex escapements. Recently, George Daniels developed a so-called “coaxial” escapement.
The escapement includes the escape wheel, lever, and balance complete with hairspring.
A glass window on the case back to show the movement.
A spring metal bracelet that expands to fit different wrist sizes.
The visible side of the watch where the dial is contained. Most are printed with Arabic or Roman numerals.
FARMER’S WATCH (OIGNON)
A large pocket watch with a verge escapement an a farm scene on the dial.
A Latin work meaning “made by.”
Silver that is .999 fine or higher, meaning that it is 999 parts per 1000 pure silver.
A watch that denotes the time every five minutes, and on the hour and half hour, by operating a push piece.
The usually inclined ring that separates the crystal from the dial. The flange is sometimes equipped with features such as tachymetric scales and pulsometers.
Engraving on the dial or case of a watch, covered with an enamel layer.
Said of surfaces worked with thin parallel grooves, mostly on dials or case bezels.
Feature combined with chronograph functions, that allows a new measurement starting from zero (and interrupting a measuring already under way) by pressing down a single pusher, i.e. without stopping, zeroing and restarting the whole mechanism. Originally, this function was developed to meet the needs of air forces.
A chronograph with a special dial train switch that makes the immediate re-use of the chronograph movement possible after resetting the hands. It was developed for special timekeeping duties (such as found in aviation), which require the measurement of time intervals in quick succession. A flyback may also be called a retour en vol.
A second hand on the chronograph that can be used to time laps or to determine finishing times for several competitors in race.
A short chain or ribbon attached to a pocket watch, or pocket watch chain, and worn hanging in front of the vest or waist. An ornament or seal is typically attached to such a chain or ribbon.
Hinged and jointed element, normally of the same material as the one used for the case. It allows easy fastening of the bracelet on the wrist. Often provided with a snap-in locking device, sometimes with an additional clip or push piece.
A straight-armed balance with weights on each end used for regulation; found on the earliest clocks and watches.
The part of the pallet lever that engages with the roller jewel.
The seconds wheel in going-train.
Vibration Generally defined as the number of cycles per time unit; in horology it is the number of oscillations of a balance every two seconds or of its vibrations per second. For practical purposes, frequency is expressed in vibrations per hour (vph).
A plate (or disc) that covers the works and supports the wheels pivots. There is a top plate, a bottom plate, half and 3/4 plate. The top plate has the balance resting on it.
A conical part with a spiral groove on which a chain or cord attached to the barrel is wound. Its purpose is to equalize the driving power transmitted to the train.
The system of gears that transmits power from the mainspring to the escapement.
The art of producing a design, pattern, or wavy appearance on a metal. [This is the European term for damaskeening.]
GENEVA STOP WORK
A system used to stop the works preventing the barrel from being over wound.
A composition of nickel, copper and zinc. It contains no silver. Also known as Nickel Silver.
GILT OR GILD
To coat or plating with gold leaf or a gold color.
Watches use two different types of glass. Sapphire crystal glass is virtually scratchproof, while cheaper watches mostly use hardened mineral glass.
GLOBAL POSITIONING SYSTEM (GPS) WATCH
Watches that utilize GPS technology and provide features such as multi-channel receivers that can receive signals from many GPS satellites to calculate and display the latitude, longitude and altitude of your current position.
Bronze and beryllium alloy used for high-quality balances. This alloy assures high elasticity and hardness values; it is non-magnetic, rust proof and has a very reduced dilatation coefficient, which makes the balance very stable and assures high accuracy of the movement.
Abbreviation for Greenwich Mean Time. As a feature of watches, it means that two or more time zones are displayed. In this case, the second time may be read from a hand making a full rotation in a 24-hour ring (thereby also indicating whether it is am. or p.m. in that zone).
The barrel houses the main spring; as the spring uncoils, the barrel turns, and the teeth on the outside of the barrel turn the train of gears as opposed to toothless fusee barrel.
Sandwich-type metal; a layer of gold, a layer of base metal in the middle, and then another layer of gold – these layers of metals are soldered to each other to form a sandwich.
GOLD JEWEL SETTING
In high-grade watches the jewels were mounted in gold settings.
A layer of gold that has been electro-deposited onto a metal; its thickness is measured in microns.
Harmonic flattened bell in a steel alloy, generally positioned along the circumference of the movement and struck by hammers to indicate time by sounds. Size and thickness determine the re-suiting note and tone. In watches provided with minute-repeaters, there are often two gongs and the hammers strike one note to indicate hours, both notes together to indicate quarters and the other note for the remaining minutes. In more complex models, equipped also with en-passant sonnerie devices, there may be up to four gongs producing different notes and playing even simple melodies (such as the chime of London’s Big Ben).
The most complex of mechanical watches featuring an abundance of complications. The term is normally restricted to mechanical watches. Quartz watches with additional features are usually described as ‘multi-functional’.
The main wheel of a fusee type watch.
GRANDE SONNERIE (GRAND STRIKE)
A type of repeater that sounds the hours and quarter hours when the wearer pushes the button.
Decoration of dials, rotors or case parts consisting of patterns, made by hand or engine-turned. By the thin pattern of the resulting engravings—consisting of crossing or interlaced lines—it is possible to realize even complex drawings. Dials and rotors decorated in this way are generally in gold or in solid silver.
Surface decoration, normally on the dial, whereby a grooving tool with a sharp tip is used to cut an even pattern onto a level surface. The exact adjustment of the tool for each new path is controlled by a device similar to a pantograph, and the movement of the tool can be controlled either manually or mechanically. Real guillochis (the correct term used by a master of guilloche) are very intricate and expensive to produce, which is why most of the dials decorated in this fashion are produced by stamping machines.
A watch with a balance that can be stopped to allow synchronization with another timepiece.
The spring which vibrates the balance.
A hairspring stud is used to connect the hairspring to the balance cock.
The silver or gold or platinum markings of many countries.
Steel or brass element used in movements provided with a repeater or alarm sonnerie. It strikes a gong or bell.
Indicator for the analogue visualization in hours, minutes and seconds as well as other functions, Normally made of brass (rhodium-plated, gilded or treated otherwise), but also steel or gold. Hands are available in different shapes and take part in the aesthetic result of the whole watch.
Alpha Hands: A slightly tapered hand.
Baton Hands: A narrow hand sometimes referred to as a stick hand.
Dauphine Hands: A wide, tapered hand with a facet at the centre running the length of the hand.
Luminous Hands: Hands made of skeleton form with the opening filled by a luminous material.
Skeleton Hands: Cut-out hands showing only the frame.
A scratch resistant metal comprised of binding several materials, including titanium and tungsten carbide, which are then pressed into an extremely hard metal and polished with diamond powder to add brilliance.
HEART-PIECE HEART CAM-PIECE
A heart shaped cam which causes the hand on a chronograph to fly back to zero.
A cylindrical spring used in chronometers.
Valve inserted in the case of some professional diving watches to discharge the helium contained in the air mixture inhaled by divers.
An artificial glass made of a plastic resin.
Used as a protective shield for spacecraft reentering the earth’s atmosphere, high-tech ceramic is polished with diamond dust to create a highly polished finish. Because the ceramic can be injection molded, pieces can be contoured. It has a very smooth surface and is usually found in black, but can be produced in a spectrum of colors.
The science of time measurement, including the art of designing and constructing the timepieces.
A caliber characterized by the seconds hand fitted on an axis perpendicular to the one of the winding stem.
A pocket watch case with a covered face that must be opened to see the watch dial.
The jewel-pin that serves as the point of contact between the time-train and the balance wheel. Also called the roller jewel.
Incabloc is a trade name for a type of shock absorbing device/spring used to protect the delicate parts of the mechanical watch escapement. Mentioned here as it is probably the most widely used and some watch manufacturers used to draw attention to it by referring to it on the watch dial itself.
A seconds hand driven independently by a separate train but controlled by the time train.
Another term for the racquet-shaped regulator which lengthens or shortens the effective length of the hairspring.
A watch bracelet that is integrated into the design of the case.
“Isos” means equal; chronos means time-occuring at equal intervals of time. The balance and hairspring adjusted will allow the watch to run at the same rate regardless whether the watch is fully wound or almost run down.
Precious stone used in movements as a bearing Generally speaking, pivots of wheels in movements turn inside synthetic jewels (mostly rubies) lubricated with a drop of oil. The jewel’s hardness reduces wear to a minimum even over long periods of time (50 to 100 years). The quality of watches is determined mainly by the shape and finishing of jewels rather than by their number (the most refined jewels have rounded holes and walls to greatly reduce the contact between pivot and stone).
Feature concerning the digital display of time in a window. The indication changes almost instantaneously at every hour.
An invention of Bonniksen in 1894 which allows the entire escapement to revolve within the watch once in 52 1/2 minutes (in most karrusels),. this unit is supported at one end only as opposed to the tourbillon which is supported at both ends and which most often revolves about once a minute.
Older watch that had to be set with a key.
A trade name for a shock absorbing system; in a similar vein to Incabloc above.
Seiko Kinetic? watches run entirely on self generated energy from natural movement of your wrist. It never needs a battery, being independent of conventional storage batteries.
The ability, in some quartz sport watches, to preserve in the watch’s memory the times of laps in a race that have been determined by the lap timer. The wearer can recall these times on a digital display by pushing a button.
A chronograph function that lets the wearer time segments of a race. At the end of a lap, the wearer stops the timer, which then returns to zero to begin timing the next lap.
Leap or bissextile years have 366 days and occur every 4 years (with some exceptions, Calendar, Gregorian). Some watches display this datum.
The teeth of the pinion gears.
A caliber typical for pocket-watches, characterized by the seconds hand fitted in the axis of the winding-stem
Swiss term for open face. Introduced by J.A. L’Epine in 1770.
Invented by Thomas Mudge in 1760.
The lever used to set some watches.
LIGHT-EMITTING DIODE (LED)
A type of diode that emits light when current passes through it. LEDs have many uses, visible LEDs are used as indicator lights on all sorts of electronic devices (including pocket watches and wristwatches.)
Ancient French measuring unit maintained in horology to indicate the diameter of a movement. A line (expressed by the symbol “‘) equals 2.255mm. Lines are not divided into decimals; therefore, to indicate measures inferior to the unit, fractions are used (e.g. movements of 13″‘3/4 or 10″‘1/2).
LIQUID-CRYSTAL DISPLAY (LCD)
A digital watch display that shows the time electronically by means of the liquid held in a thin layer between two transparent plates.
Arresting the advance of the escape wheel during the balance’s free excursion.
To reduce friction caused by the running of wheels and other parts. There are points to be lubricated with specific low-density oils such as the pivots turning inside jewels, the sliding areas between levers, and the spring inside the barrel (requiring a special grease), as well as numerous other parts of a movement.
Double extension of the case middle by which a strap or bracelet is attached. Normally, straps and bracelets are attached with removable spring bars.
Said of materials applied on markers and/or hands, emitting the luminous energy previously absorbed as electromagnetic light rays. Tritium is no longer used and was replaced by other substances having the same emitting powers, but with virtually zero radioactivity, such as Super-LumiNova and Lumibrite.
Emitting light, especially emitting self-generated light. (Used on watch hands and hour markers.)
Base plate on which all the other parts of the watch movement are mounted.
This and the barrel make up the driving element of a movement. It stores and transmits the power force needed for its functioning.
The first driving wheel, part of the barrel.
The part of the stop works preventing the barrel from being over wound.
A mechanical movement in which winding is performed by hand. The motion transmitted from the user’s fingers to the crown is forwarded to the movement through the winding stem, from this to the barrel through a series of gears and finally to the mainspring.
A watch company that uses a movement” in at least one of its models that it has manufactured itself on its own premises.
A large-sized watch enclosed in a box (therefore also called box chronometer) mounted on gimbals and used, on board of ships, to determine the respective longitude.
Highly accurate mechanical or electronic timekeeper enclosed in a box (hence the term “box chronometer”), used for determining the longitude on board a ship. It is necessary for marine chronometers with mechanical movements to be mounted on gimbals so that they remain in a horizontal position.
Elements printed or applied on the dial, sometimes they are luminescent, used as reference points for the hands to indicate hours and fifteen- or five-minute intervals.
The mean time of the meridian of the Greenwich Observatory, considered the universal meridian, is used as a standard of the civil time system, counted from midnight to midnight.
Also equal hours; average solar time; the time shown by watches.
MEAN TIME SCREWS
Balance screws used for timing, usually longer than other balance screws; when turned away from or toward the balance pin, they cause the balance vibrations to become faster or slower.
A feature, usually consisting of a graduated scale on a watch’s bezel, that lets the wearer translate one type of measurement into another; for example, miles into kilometers, or pounds into kilograms.
A movement powered by a mainspring, working in conjunction with a balance wheel.
Element positioned on the regulator, allowing to shift it by minimal and perfectly gauged ranges so as to obtain accurate regulations of the movement.
A regulator used on railroad grade watches to adjust for gain and loss in a very precise way.
A millionth of a second.
Unit of measure of the thickness of the gold-plating. 1 micron = 1/1000mm.
A striking mechanism with hammers and gongs for acoustically signaling the hours, quarter hours, and minutes elapsed since noon or midnight. The wearer pushes a slide, which winds the spring. Normally a repeater uses two different gongs to signal hours (low tone), quarter hours (high and low tones in succession), and minutes (high tone). Some watches have three gongs, called a carillon.
Self-contained mechanism, independent of the basic caliber, added to the movement to make an additional function available: chronograph, power reserve, GMT, perpetual or full calendar.
A function available in many watches, usually combined with calendar-related features ~ The moonphase disc advances one tooth every 24 hours. Normally, this wheel has 59 teeth and assures an almost perfect synchronization with the lunation period, i.e. 29.53 days (in fact, the disc shows the moonphases twice during a single revolution). However, the difference of 0.03 PAWL days, i.e. 44 minutes each month, implies the need for a manual adjustment every two and a half years to recover one day lost with respect to the real state of moonphase. In some rare case, the transmission ratio between the gears controlling the moonphase are calculated with extreme accuracy so as to require manual correction only once in 100 years.
Iridescent milky interior shell of the freshwater mollusk that is sliced thin and used on watch dials. While most have a milky white luster, mother-of-pearl also comes in other colors such as silvery gray, gray blue, pink and salmon.
The entire mechanism of a watch. Movements are divided into two great families: quartz and mechanical; the latter are available with manual or automatic winding devices.
A watch that plays a tune on demand or on the hour.
Different colors of gold – red, green, white, blue, pink, yellow and purple.
One billionth of a second.
The National Association of Watch and Clock Collectors. Located: 514 Popular Street, Columbia, Pennsylvania 17512 (telephone: 1-717-684-8261.) Founded in 1943, The National Association of Watch and Clock Collectors, Inc. (NAWCC) is a nonprofit scientific organization that serves as a unique educational, cultural and social resource for its membership and the public at large. Members include hobbyists, students, educators, casual collectors, and professionals in related retail and manufacturing trades. The one common bond (and main membership requirement) is a fascination with the art and science of timekeeping (horology).
Trade name (from the producer’s name) of a steel alloy, resisting magnetization, used for modern self-compensating balance springs. The quality level of this material is indicated by the numeral following the name in decreasing value from 1 to 5.
Nickname for a German watch that was oval-shaped.
An observatory-tested precision watch that obtained the relevant rating certificate.
Large older (1700s) style watch in the shape of a onion or in the shape of a bulb.
A small well around a pivot which retains oil.
O rings are used to seal the backs of watches which feature either a press-in back or a screw on back. They ensure water resistance. Usually also used on the winding stems of watches and in the winding crowns to protect against the ingestion of water and dust. Normally made from a rubber/plastic compound.
Complete oscillation or rotation movement of the balance, formed by two vibrations.
A lever escapement error; the roller jewel passes to the wrong side of the lever notch, causing one side of the pallet to rest against the banking pin and the roller jewel t rest against the other side, thus locking the escapement and stopping the motion of the balance.
The raised up portion of the balance hairspring, not flat. Also called Breguet hairspring.
Device of the escapement transmitting part of the motive force to the balance, in order to maintain the amplitude of oscillations unchanged by freeing a tooth of the escape wheel at one time. Lever with a beak that engages in the teeth of a wheel under the action of a spring.
Oxidation of any surface and change due to aging. A natural staining or discoloration due to the aging process.
An extra case around a watch (two cases), hence a pair of cases. The outer case kept out the dust. The inner case could not be dustproof because it provided the access to the winding and setting keyholes in the watch case.
One of six platinum metals, used in watches in place of platinum, because it is harder, lighter and cheaper.
An early shock proofing system designed to fit as a spring on the end stone of balance.
A number of jewels or stone set close together. Paved in diamonds.
A device that counts the number of strides taken by the wearer by responding to the impact of the wearer’s steps.
The neck of the watch; attached to it is the bow (swing ring) and the crown. The portion of the watch which holds the winding-stem and crown.
A watch that uses the pendant to set the watch. See also “Lever-set”.
The calendar module for this watch type automatically makes allowances for the different lengths of each month as well as leap years. A perpetual calendar also usually shows the date, month, and four-year cycle, and may show the day of the week and moon phase as well.
PILLAR-PLATE OR MAIN PLATE
Supporting element of bridges and other parts of a movement.
A metal similar in appearance to gold. named after the inventor. Alloy of four parts copper and three parts zinc.
Combines with a wheel and an arbor to form a gear. A pinion has less teeth than a wheel and transmits motive force to a wheel. Pinion teeth (normally 6 to 14) are highly polished to reduce friction to a minimum.
End of an arbor turning on a jewel support. As their shape and size can influence friction, the pivots of the balance-staff are particularly thin and, hence, fragile, so they are protected by a shockproof system.
A watch has a front and a back plate or top and bottom plate. The works are in between.
Said of a metal treated by a galvanizing procedure in order to apply a slight layer of gold or another precious metal (silver, chromium, rhodium or palladium) on a brass or steel base.
One of the rarest of precious metals, platinum also is one of the strongest and heaviest, making it a popular choice for setting gemstone jewelry and watches. It has a rich, white luster, and an understated look. Platinum is hypoallergenic and tarnish resistant. Platinum used in jewelry and watches is at least eighty-five to ninety-five percent pure. Many platinum watches are produced in limited editions due to the expense and rarity of the metal.
A synthetic resin used for watch crystal.
POIN-ON DE GENEVE
Distinction assigned by the Canton of Geneva to movements produced by watchmaker firms of the Region and complying with all the standards of high horology with respect to craftsmanship, small-scale production, working quality, accurate assembly and setting. The Geneva Seal is engraved on at least one bridge and shows the Canton’s symbol, i.e. a two-field shield with an eagle and a key respectively in each field.
A term meaning in balance to equalize the weight around the balance.
PONTILLAGE (BULL’S EYE CRYSTAL)
The grinding of the center of a crystal to form a concave or so called “bull’s eye crystal.”
Pop Art is a 20th century art movement that utilized the imagery and techniques of consumerism and popular culture. Pop art developed in the late1950’s as a reaction against Abstract Expressionism and flourished in the sixties and early seventies. Pop Art favored figural imagery and the reproduction of everyday objects, such as Campbell Soup cans, comic strips and advertisements. The movement eliminated distinctions between “good” and “bad” taste and between fine art and commercial art techniques.
As adjusted to five positions; a watch may differ in its time keeping accuracy as it lays in different positions. Due to the lack of poise, changes in the center of gravity, a watch can be adjusted to six positions: dial up, dial down, stem up, stem down, stem left and stem right.
POWER RESERVE POWER RESERVE INDICATOR
Duration (in hours) of the residual functioning autonomy of a movement after it has reached the winding peak. The duration value is displayed by an instantaneous indicator: analog (hand on a sector) or digital (through a window). The related mechanism is made up of a series of gears linking the winding barrel and hand. Recently, specific modules were introduced which may be combined with the most popular movements.
Accuracy rate of a watch, a term difficult to define exactly. Usually, a precision watch is a chronometer whose accuracy-standard is certified by an official watch-rating bureau, and a high-precision watch is a chronometer certified by an observatory.
The pulsimeter scale shows, at a glance, the number of pulse beats per minute. The observer releases the chronograph hand when starting to count the beats and stops at the 30th, the 20th or the 15th beat according to the basis of calibration indicated on the dial.
Scale on the dial, flange, or bezel that, in conjunction with the second hand, may be used to measure a pulse rate. A pulsometer is always marked with a reference number; if it is marked, for example gradue pour 15 pulsations then the wearer counts 15 beats of a pulse. At the last beat, the second hand will show what the pulse rate is in beats per minute on the pulsometer scale.
PUSHER, PUSH-PIECE OR PUSH BUTTON
Mechanical element mounted on a case for the control of specific functions. Generally, pushers are used in chronographs, but also with other functions.
Abbreviation of Physical Vapor Deposition, a plating process consisting of the physical transfer of substance by bombardment of electrons.
A watch with five beats or more per second or 18,000 per hour.
Timekeeping’s technical revolution found its way to the world’s wrists in the late 1960s. This was a principally Swiss invention – the first working quartz wristwatches were manufactured by Girard-Perregaux and Piaget as the result of an early joint venture within the Swiss watch industry, but the Japanese (primarily Seiko) came to dominate the market with new technology. The quartz movement uses the famously stable vibration frequency of a quartz crystal subjected to electronic tension (usually 32,868 Hz) as its norm. The fact that a quartz-controlled second hand jumps to the tact of each second is a concession to the use of outside energy.
A tiny piece of synthetic quartz that oscillates at the rate of 32.768 times a second, dividing time into equal segments.
A movement powered by a quartz crystal to vibrate.
RACK & PINION LEVER ESCAPEMENT
Developed by Abbe de Huteville in 1722 and by Peter Litherhead in 1791; does not use a roller table, but a pinion.
Toothed wheel prevented from moving by a click pressed down by a spring.
Used to describe the split seconds chronograph (seeFlyback) which has two seconds hands sitting atop one another. On depression of a third chronograph button (most have two), the flyback hand will stop in order to measure say, a lap time; repressing this button with cause the flyback hand to flyback(!) to the other seconds hand which has remained in motion.
Also called left or entrance jewel, the first of tow pallet jewels with which a tooth of the escape wheel comes into engagement.
Made up by balance and balance spring, governing the division of time within the mechanical movement, assuring its regular running and accuracy. As the balance works like a pendulum, the balance spring’s function consists of its elastic return and starting of a new oscillation. This combined action determines the frequency, i.e. the number of vibrations per hour, and affects the rotation speed of the different wheels. In fact the balance, by its oscillations, at every vibration (through the action of the pallets), frees a tooth of the escape wheel (Escapement). From this, motion is transmitted to the fourth wheel, which makes a revolution in one minute, to the third and then the center wheel, the latter making a full rotation in one hour. However, everything is determined by the correct time interval of the oscillations of the balance.
Regulating the functioning of a movement by lengthening and shortening the active section of the balance spring. It is positioned on the balance-bridge and encompasses the balance spring with its two pins near its fixing point on the bridge itself. By shifting the index, the pins also are moved and, by consequence, the portion of the balance spring capable of bringing the balance back is lengthened or shortened by its elastic force. The shorter it is, the more reactive it tends to be and the more rapidly it brings the balance back and makes the movement run faster. The contrary happens when the active portion of the balance spring is lengthened. Given today’s high frequencies of functioning, even slight index shifts entail daily variations of minutes. Recently, even more refined index-regulation systems were adopted (from eccentric to micrometer screws) to limit error margins to very few seconds per day.
Old term used to denote any mechanism assuring a constant transmission of the driving power to the escape wheel.
Mechanism indicating time by acoustic sounds. Contrary to the watches provided with en-passent sonnerie devices, that strike the number of hours automatically, repeaters work on demand by actuating a slide or pusher positioned on the case side. Repeaters are normally provided with two hammers and two gongs: one gong for the minutes and one for the hours. The quarters are obtained by the almost simultaneous strike of both hammers. The mechanism of the striking work is among the most complex complications.
A watch with a hammered, raised decoration on the case.
Said of a hand that, instead of making a revolution of 360 before starting a new measurement, moves on an arc scale (generally of 90 to 180) and at the end of its trip comes back instantaneously. Normally, retrograde hands are used to indicate date, day or month in perpetual calendars, but there are also cases of retrograde hours, minutes or seconds. Unlike the case of the classical indication over 360, the retrograde system requires a special mechanism to be inserted into the basic movement.
An unconventional modern style of fashionable design, or dress (originated in the 1960s.) Refers to the fashion, decor, design, or style reminiscent of things from the past (especially from the 1960s.)
RIGHT ANGLE ESCAPEMENT
Also called English Escapement.
Thin layer of gold soldered to a base metal.
The jewel mounted or seated in the roller table, which receives the impulse from the pallet fork.
ROLLER TABLE OR ROLLER
Part of the escapement in the shape of a disc fitted to the balance staff and carrying the impulse pin that transmits the impulses given by the pallets to the balance.
Developed by the Romans for use in trade and commerce as a method to indicate numbers. Roman numerals were very popular on yesteryear’s pocket watches and clocks and are sometimes used on today’s wristwatches, clocks and pocket watches.
I – (Roman symbol for 1)
V – (Roman symbol for 5)
X – (Roman symbol for 10)
L – (Roman symbol for 50)
C – (Roman symbol for 100)
D – (Roman symbol for 500)
M – (Roman symbol for 1000)
ROSE (OR PINK) GOLD
A softly hued gold that contains the same metals as yellow gold but with a higher concentration of copper in the alloy. A popular color in Europe, rose gold in watches is often seen in retro styling or in tricolor gold versions. Some 18k red gold watches achieve their color from additional copper in the alloy.
A complicated case design with a practical raison d’etre, (first and famously invented by Jaeger le Coultre to protect the glass and dial from damage on the polo field or hunting field) where the case can be reversed so that the case back is uppermost.
A bezel (the ring surrounding the watch face) that can be turned. Different types of rotating bezels perform different timekeeping and mathematical functions.
In automatic-winding mechanical movements the rotor is the part that, by its complete or partial revolutions and the movements of human arm, allows winding of the mainspring.
A pinion in the center wheel designed to unscrew if the mainspring breaks; this protects the train from being stripped by the great force of the mainspring.
The smaller of the two rollers in a double roller escapement.
A crystal (the cover that protects the watch face) made of synthetic sapphire, a transparent shatter-resistant, scratch-resistant substance.
Combination of sapphire and hardlex crystals.
Graduation on a measuring instrument, showing the divisions of a whole of values, especially on a dial, bezel. The scales mostly used in horology are related to the following measuring devices: tachometer (indicating the average speed), telemeter (indicating the distance of a simultaneously luminous and acoustic source, e.g. a cannon-shot or a thunder and related lightning), pulsometer (to calculate the total number of heartbeats per minute by counting only a certain quantity of them). For all of these scales, measuring starts at the beginning of the event concerned and stops at its end; the reading refers directly to the chronograph second hand, without requiring further calculations.
Before the invention of the perfectly weighted balance by use of a smooth ring, balances were fitted with weighted screws to get the exact impetus desired. Today a screw balance is a subtle sign of quality in a movement due to its costly construction.
A crown that can be screwed into the case to make the watch watertight.
SECOND TIME-ZONE INDICATOR
An additional dial that can be set to the time in another time zone. It lets the wearer keep track of local time and the time in another country simultaneously.
The skin of a horse, a shark, ray fish and other animal usually dyed green or blue green. Then used as ornamental covers for older watch cases.
Resilient bearing which, in a watch, is intended to take up the shocks received by the balance staff and thus protects its delicate pivots from damage.
SHOCKPROOF OR SHOCK-RESISTENT
Watches provided with shock-absorber systems (e.g. Incabloc) help prevent damage from shocks to the balance pivots. Thanks to a retaining spring system, it assures an elastic play of both jewels, thus absorbing the movements of the balance-staff pivots when the watch receives strong shocks. The return to the previous position is due to the return effect of the spring. If such a system is lacking, the shock forces exert an impact on the balance-staff pivots, often causing bending or even breakage.As defined by the U.S. government regulation, a watch’s ability to withstand an impact equal to that of being dropped onto a wood floor from a height of three feet.
A metal grill that covers the crystal. They were mainly used during World War 1 to protect watches from shrapnel and other flying debris.
The time of rotation of the Earth as measured from the stars. About 3 minutes 56 seconds shorter than the mean solar day.
The conventional time standard refers to the sidereal year (defined in terms of an average of 365.25636 days) considered to be perfectly regular until very recently, but — even though this is not true — the difference is so slight that it is virtually neglected. As a unit of time, the sidereal day is used mainly by astronomers to define the interval between two upper transits of the vernal point in the plane of the meridian.
A mismatched case and movement; a term used for a hunting movement that has been placed on an open face case and winds at the 3 o’clock position. Open face cases wind at the 12 o’clock position.
A type of case composed of alloys to simulate the appearance of silver.
The safety roller and the roller jewel are one single table.
System used to determine the size of the movement to the case.
Watches whose bridges and pillar-plates are cut out in a decorative manner, thus revealing all the parts of the movement.
A case with a transparent front or back that allows the wearer to view the watch’s movement.
A watch made so the viewer can see the works. Plates are pierced and very decorative.
An antique watch that is hinged at the jaw to reveal a watch.
A device consisting of a logarithmic or other scale on the outer edge of the watch face that can be used to do mathematical calculations.
A watch with four beats per second or 14,000 per hour.
A cam shaped much like a snail. The snail determines the number of blows to be struck by a repeater (a count wheel.)
Decoration with a spiral pattern, mainly used on the barrel wheel or on big-sized full wheels.Ornamentation of the surface of metals by means of a circle design; also called damaskeening.
A compass that allows the wearer to determine the geographical poles by means of a rotating bezel. The wearer places the watch so that the hour hand faces the sun. Then, the wearer takes half the distance between the position and 12 o’clock, and turns the bezel until its “south” marker is at that halfway point. Some quartz watches have solar compasses that show directions on an LCD display.
SOLAR POWERED BATTERIES
Batteries in a quartz watch that are recharged via solar panels on the watch face.
Generally speaking, the time standard referred to the relative motion of the Earth and the Sun governing the length of day and night. The true solar day is the period measured after the Sun appears again in the same position from our point of observation. Due to the non-uniform rotation of the Earth around the Sun, this measure is not regular. As an invariable measure unit, the mean solar day corresponds to the average duration of all the days of the year.
365 days, 5 hours, 48 minutes and 49.7 seconds.
A watch with no moving parts. All digital watches are 100% solid state, whilst analogue watches combine solid state circuits with moving parts.
The time when the sun is farthest from the equator, i.e. on June 21st (Summer solstice) and December 21st (Winter solstice).
SONNERIE (EN PASSANT)
The cheapest Brequet watch which he make with high quality made in batches or group lots in advance to lower the cost (ebauches.)
SPACE AGE WATCH
Watch making designs (especially from 1957 to 1979) that reflect the bold and daring styles that emerged from the technology that was derived from the space travel revolution.
SPLIT SECONDS HAND
Actually two hands, one a fly-back hand, the other a regular chronograph hand. When the wearer starts the chronograph, both hands move together. To time laps or different finishing times, the wearer can stop the fly-back hand independently while the regular chronograph hand keeps moving, in effect ‘splitting’ the hand(s) in two.
Chronographs with split-second mechanisms are particularly useful for timing simultaneous phenomena which begin at the same time, but end at different times, such as sporting events in which several competitors are taking part. In chronographs of this type, an additional hand is superimposed on the chronograph hand. Pressure on the pusher starts both hands, which remain superimposed as long as the split-second mechanism is not blocked. This is achieved when the split-second hand is stopped while the chronograph hand continues to move. After recording, the same pusher is pressed a second time, releasing the split-second hand, which instantly joins the still-moving chronograph hand, synchronizing with it, and is thus ready for another recording. Pressure on the return pusher brings the hands back to zero simultaneously, provided the split-second hand is not blocked. Pressure on the return pusher brings the hands back to zero simultaneously, provided the split-second hand is not blocked. Pressure on the split pusher releases the split second hand, which instantly joins the chronograph hand if the split-second hand happens to be blocked.
A watch with two second hands, one of which can be stopped with a special dial train lever to indicate an intermediate time while the other continues to run. When released, the split-seconds hand jumps ahead to the position of the other second hand. This type of chronograph is also called a rattrapante.
Decoration used on a watch movement and barrel of movements.
The metal keeper that attaches the band to the lugs of a wrist watch and is spring loaded.
A circular tube housing a coiled type spring.
Curved spring and cam to equalize the uneven force of the mainspring on the 16th century German movements.
Name for the axle of the balance.
An extremely durable metal alloy (chromium is a main ingredient) that is virtually immune to rust, discoloration and corrosion; it can be highly polished, to look like a precious metal. Because of its strength, stainless steel is often used even on case backs of watches made of other metals.
A shape or design with emanating rays that resembles the flash of light produced by an exploding star.
The part of a quartz movement that moves the gear train, which in turn moves the watch’s hands.
A white and highly reflective precious metal. Sterling silver refers to silver that is 92.5 percent pure, which should be stamped on the metal, sometimes accompanied by the initials of the designer or the country of origin as a hallmark. Although less durable than stainless steel and other precious metals, sterling silver is often employed in watches that coordinate or look like sterling silver jewelry. A protective coating may be added to prevent tarnish.
Traditional device (now obsolete) provided with a finger piece fixed to the barrel arbor and a small wheel in the shape of a Maltese cross mounted on the barrel cover, limiting the extent to which the barrel can be wound.
A watch with a second hand that measures intervals of time. When a stopwatch is incorporated into a standard watch, both the stopwatch function and the timepiece are referred to as a “chronograph.”
A small dial on the watch face used for any of several purposes, such as keeping track of elapsed minutes or hours on the chronograph, or indicating the date.
A devise using a gnomon or style that cast a shadow over a graduated dial as the sun progresses, indicating solar time.
Using a patented integrated circuit technology, some watches are capable of assuring their accuracy up to 20 times more accurate than conventional quartz watches, being accurate to ±10 seconds per year.
SWEEP SECOND HAND
A center second hand, i.e. a second hand mounted on the center of the main dial.
A watch is considered Swiss if its movement was assembled, started, adjusted and controlled by the manufacturer in Switzerland.
SWISS A.O.S.C. (CERTIFICATE OF ORIGIN)
A mark identifying a watch that is assembled in Switzerland with components of Swiss origin.
TACHOMETER OR TACHYMETER
Function measuring the speed at which the wearer runs over a given distance. The tachometer scale is calibrated to show the speed of a moving object, such as a vehicle, over a known distance. The standard length on which the calibration is based is always shown on the dial, e.g. 1,000, 200 or 100 meters, or—in some cases—one mile. As the moving vehicle, for instance, passes the starting-point of the measured course whose length corresponds to that used as the basis of calibration, the observer releases the chronograph hand and stops it as the vehicle passes the finishing point. The figure indicated by the hand on the tachometer scale represents the speed in kilometers or miles per hour.
A scale on the dial, flange, or bezel of a chronograph that, in conjunction with the second hand, gives the speed of a moving object. A tachymeter takes a value determined in less than a minute and converts it into miles per hour. For example, a wearer could measure the time it takes a car to pass between two mile markers on the highway. When the car passes the second marker, the second hand will be pointing to the car’s speed in miles per hour on the tachymetric scale.
A tang buckle is a traditional Loop & Pin (belt type) buckle.
A rectangular watch designed by Louis Cartier. The bars along the sides of the watch were inspired by the tracks of tanks used in World War 1.
By means of the telemeter scale, it is possible to measure the distance of a phenomenon that is both visible and audible. The chronograph hand is released at the instant the phenomenon is seen; it is stopped when the sound is heard, and its position on the scale shows, at a glance, the distance in kilometers or miles separating the phenomenon from the observer. Calibration is based upon the speed at which sound travels through the air, viz, approximately 340 meters or 1,115 feet per second. During a thunderstorm, the time that has elapsed between the flash of lightning and the sound of the thunder is registered on the chronograph scale.
Wheel positioned between the minutes and seconds wheels.
THIRTY (30) MINUTE RECORDER (OR REGISTER)
A subdial on a chronograph that can measure time periods of up to 30 minutes.
The 24 equal spherical lines unto which the surface of the Earth is conventionally divided, each limited by two meridians. The distance between two adjacent zones is 15~ or 1 hour. Each country adopts. the time of its zone, except for countries with more than one zone. The universal standard time is that of the zero zone whose axis is theGreenwich meridian.
Instrument used for registering intervals of time (duration, brief times), without any indication of the time of day.
A “space age” metal, often having a silver-gray appearance. Because it is 30 percent stronger and nearly 50 percent lighter than steel, it has been increasingly used in watchmaking, especially sport watch styles. Its resistance to salt water corrosion makes it particularly useful in diver’s watches. Since it can be scratched easily, some manufacturers use a patented-coating to resist scratching.
Particular shape of a watchcase, imitating the profile of a barrel, i.e. with straight, shorter, horizontal sides and curved, longer, vertical sides.
The metal plate that usually contains the name and serial number.
A twisting force.
A mechanism that keeps track of elapsed time and displays it, usually on a subdial.
Device invented in 1801 by A. L. Breguet. This function equalizes position errors due to changing positions of a watch and related effects of gravity. Balance, balance spring and escapement are housed inside a carriage, also called a cage, rotating by one revolution per minute, thus compensating for all the possible errors over 360. Although this device is not absolutely necessary for accuracy purposes today, it is still appreciated as a complication of high-quality watches.
A technically demanding device to compensate for the interference of gravity on the balance and thus improve a watch’s rate. In a tourbillon (from the French word for whirl), the entire escapement is mounted on an epicyclic train in a “cage” and rotated completely on its axis over regular periods of time, usually once a minute. Today this superb technical delicatesse is a sign of the highest quality.
All the wheels between barrel and escapement.
A series of gears that form the works of a watch. The train is used for other functions such as chiming. The time train carries the power to the escapement.
Watches sold with both key and stem-winding on the same movement.
Also, denotes watches that were converted from pocket watches to wristwatches in the early 1900s. During the 1800’s pocket watches were all that was available. The wristwatch had not yet been used. A popular story from the early 1900s tells of a German military officer strapping his pocket watch to his wrist to keep his hands free. This was the beginning of the modern wristwatch. As this practice became popular, smaller sized pendant or pocket watches were adapted for use on the wrist. This is where the term “transition” watch is commonly used. When wristwatch popularity amongst men really took off (1908 to 1915), everyone wanted to join in on the fad. Watch factories took existing smaller smaller pocket watches and retrofitted them into a wristwatch. And, local jewelers also designed pocket watches so they could be worn on the wrist. This was quite common during the “Transitional” period.
TRIPLE CASE WATCH
18th and 19th century verge escapement, fusee watches made for the Turkish market. A fourth case sometimes added is called Quadruple cases.
Slightly radioactive material that collects light energy and is used to coat hands, numerals, and hour markers on watch dials in order to make reading the time in the dark possible. Watches bearing tritium must be marked as such, with the letter T on the dial near 6 o’clock. It is gradually being replaced by nonradioactive materials such as Superluminova and Traser due to medical misgivings and expected governmental regulation of its use.
TWELVE (12) HOUR RECORDER (OR REGISTER)
A subdial on a chronograph that can record time periods of up to 12 hours.
UNI-DIRECTIONAL ROTATING BEZEL
An elapsed time rotating bezel, often found on divers’ watches, that moves only in a counterclockwise direction. It is designed to prevent a diver who has unwittingly knocked the bezel off its original position from overestimating his or her remaining air supply. Because the bezel moves in only one direction, the diver may err only on the side of safety when timing a dive. Many divers’ watches are ratcheted, so that they lock into place for greater safety.
The mean solar time of the Greenwich meridian, counted from noon to noon, Often confused with the mean time notion.
UP AND DOWN DIAL INDICATOR
A dial that shows how much of the mainspring is spent and how far up or down the mainspring is.
Is a Swiss manufacturer of mechanical watch movements that specializes primarily in chronograph production (originally marked as VAL or “R” for Valjoux.) They are used in a number of middle range mechanical watches, and have been owned by ETA for a number of years. ETA now stamps their name on each movement. Major watch brands that use the movements are Omega, Breitling, Oris, TAG Heuer, and so on.
In horology the term is usually referred to the variation of the daily rate, i.e. the difference between two daily rates specified by a time interval.
Movement of a pendulum or other oscillating bodies, limited by two consecutive extreme positions. In an alternate (pendulum or balance) movement, a vibration is a half of an oscillation. The number of hourly vibrations corresponds to the frequency of a watch movement, determined by the mass and diameter of a balance and the elastic force of the balance spring. The number of vibrations per hour (vph) determines the breaking up of time (the “steps” of a second hand). For instance, 18,000 vph equals a vibration duration of 1/5 second; in the same way 21,600 vph = 1/6 second; 28,800 vph = 1/8 second; 36,000 vph = 1/10 second. Until the 1950s, wristwatches worked mostly at a frequency of 18,000 vph; later, higher frequencies were adopted to produce a lower percentage of irregularities to the rate. Today, the most common frequency adopted is 28,800 vph, which assures a good precision standard and less lubrication problems than extremely high frequencies, such as 36,000 vph.
The ring-shaped balance swings around its own axis and acts as the ruling organ of the movement’s escapement. The amplitude (normally about 300 degrees) is restricted by the very thin balance spring, which also provides for the reversing of the direction of rotation. The frequency of the alternating vibrations is measured in Hertz (Hz) or in the more usual vibrations per hour (vph), which is also sometimes written as A/h, the A standing for the French alternance (change). Most of today’s wristwatches tick at frequencies of 28,800 vph (4 Hz) or 21,600 vph (3 Hz). Less usual, but still found in certain models, are vibration frequencies of 18,000 vph (2.5 Hz) and 36,000 vph (5 Hz).
Early type of escapement with a wheel that is shaped like a crown.
Gold plated over silver.
Early escapement introduced in the mid 1700s.
WATCH GLASS PROTECTOR
A snap on metal grill that covers the crystal.
A disc of paper with the name of the watchmaker or repairman printed on it; used as a form of advertising and found in some pair-cased watches.
WATER RESISTENT OR WATERPROOF
A watch whose case is designed in such a way as to resist infiltration by water (3 atmospheres, corresponding to a conventional depth of 30 meters; 5 atmospheres, corresponding to a conventional depth of 50 meters.)
The ability to completely exclude the possibility of water entering into any working portion of a watch. According to the Federal Trade Commission, no watch is fully 100 percent waterproof and no manufacturer that sells watches in the U.S. may label any of their watches “waterproof.” The FTC demands that watches only be referred to as “water resistant.”
Watches come in different water resistant depths and diver’s depths:
Water resistant: Will withstand splashes of water or rain but should not be worn while swimming or diving.
Water tested to 50 meters: 5ATM: 5bar: Suitable for showering or swimming in shallow water.
Water tested to 100 meters: 10ATM: 10bar: Suitable for swimming or snorkeling.
Water tested to 150 meters: 15ATM: 15bar: Suitable for snorkeling.
Water tested to 200 meters: 20ATM: 20bar: Suitable for skin diving.
Diver’s to 150 meters—Meets ISO Standards and is suitable for scuba diving.
Diver’s to 200 meters—Meets ISO Standards and is suitable for scuba diving.
Circular element, mostly toothed, combines with an arbor and a pinion to make up a gear. Wheels are normally made of brass, while arbors and pinions are made of steel. The wheels between barrel and escapement make up the so-called train.
Created from yellow gold by incorporating either nickel or palladium to the alloy to achieve a white color. Many watches made of white gold will be 18k, or 75 percent pure gold.
An analogue watch that is able to display digital functions at the touch of a button. An easily legible white numeric display appears on the inside surface of the crystal when any digital function is activated.
A watch that indicates how much of the mainspring is spent.
Operation consisting of tightening the mainspring of a watch. This can be done by hand (by the crown) or automatically (by a rotor, which is caused to swing by the movements of the wearer’s arm).
Element transmitting motion from the crown to the gears governing manual winding and setting.
The button on the right side of the watchcase used to wind the mainspring. Also called a “crown.”
Aperture in the dial, that allows reading the underlying indication, mainly the date, but also indications concerning a second zone’s time or jumping hour.
A winding wheel’s teeth so named to their shape.
Additional feature of watches provided with a GMT function, displaying the 24 time zones on the dial or bezel, each zone referenced by a city name, providing instantaneous reading of the time of any country.
WORLD TIME DIAL WORLD TIME COMPLICATION
A dial, usually on the outer edge of the watch face, which tells the time up to 24 time zones around the world. The time zones are represented by the names of cities printed on the bezel or dial. The wearer reads the hour in a particular time zone by looking at the scale next to the city that the hour hand is pointing to. The minutes are read as normal. Watches with this feature are called “world timers.”
A countdown timer that sounds warning signals during the countdown for a boat race.
The traditionally popular gold used in all gold, gold and stainless steel combinations, or other precious metal watches.
Circular belt with the ecliptic in the middle containing the twelve constellations through which the sun seems to pass in the course of a year.
Small additional dial or indicator that may be positioned, or placed off-center on the main dial, used for the display of various functions (e.g. second counters).
Yet another reference to GMT and UTC! The use of this phrase is prevalent in civil aviation and military. Why Zulu? Well, Zulu is the phonetic for Z and the Z is for the Zero meridian, being that meridian passing through Greenwich.
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