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Glossary of Watch Terms


The opposite of digital. This means that the watch is showing the time by using hands, instead of digital numbers as in digital watches, often with floating crystals (lcd).


ATM (atmospheric pressure) is the pressure of the Earth's atmosphere and it is used to show the amount of pressure a watch can withstand under water. When a watch is under water it is subjected to pressure. One ATM watch will withstand pressures equivalent to about 10 meters. 10 ATM's is suitable for swimming, and 20 ATM's is suitable for diving.

Arabic Numerals

Arabic numerals are the numbers used in our everyday-life. Other common numerals are the Roman and the Indian numerals.

Automatic Watch

The watch is wound by the motion of the wearer's arm rather than through turning the winding stem. A rotor that turns in response to motion winds the watch's mainspring. If an automatic watch is not worn for a day or two, it will be powered by its power reserve for about three days.

Case Back

A backside of a case. There are two alternatives, either a snap case or a screw case. The case back can even be transparent leaving the movement visible (a skeleton watch).

Linear Time Display

A linear presentation of time instead of a circular as in analog watches.


The movement is mounted in the case. Even known as clockwork.

Tang Buckle

A tang buckle is the classic clasp, and is used mainly on leather, rubber and plastic bracelets. The clasp has a loop in it. It is used like a traditional leather belt.

Perpetual calendar

Watches with the perpetual calender automatically adjusts for all months and leap years.


A watch crystal is the transparent cover that protects the watch face. They are usually made of two types of material; sapphireglass or plexiglass. The more exclusive watches use more often sapphire, since it is more resistant against scratches. The advantage of plexiglass is that if it brakes, it does not shatter.


Abbreviation of Greenwich Mean Time and corresponds to the more modern term UTC (Coordinated Universal Time). GMT is the basis of every world time zone which sets the time of day and is at the centre of the time zone map. Unlike GMT, UTC uses a 24-hour format. GMT in the watch world means that the watch in question supports two time zones.


A type of engraving in which thin lines are interwoven in a pattern. A genuine Guilloche is engraved on the dial, which is a very expensive method. This is why most of the watch manufacturers often stamp it on the dial. Breguet is one of the manufacturers who still engraves the Guilloche on their watches.

Power Reserve

The time the watch will run with a fully charged power supply. The power reserve for a quatrz watch is the time between battery changes.


Hesalite is a plexiglass, used especially by Omega. The advantage is the same as with the regular plexiglass, the surface does not shatter if it brakes.

Hour Markers

Markers indicating the hours on the dial.


Jewels act as bearings for gears in a mechanical watch. The jewels reduce friction to make the watch more accurate and longer lasting. If a watch has plenty of jewels in the movement, it is of high quality.


A watch with an advanced caliber means that the watch propably has many complications, such as perpetual calender or a chronograph. The caliber also determines the length of the power reserve.


Complications are the functions of a watch. More complications means more functions. Watches with a lot of complications are also known as Grande Complication watches.


Chronograph is a watch that includes a built in stopwatch function. A timer that can be started and stopped to time an event.


A watch to be called a chronometer, it must meet certain very high standards set by the Swiss Official Chronometer Control (C.O.S.C.).


A quartz clock is a clock that uses an electronic oscillator that is regulated by a quartz crystal to keep time. Watch manufacturers use synthetic quartz crystals rather than natural ones because they have more consistent properties. Quartz watches are often very accurate.

Smiling Watch

A smiling watch is a watch displaing time ten to two or ten past ten. The hands form a "smiling" face on the dial. All the manufacturers and watch dealers display their watches as smiling.

Mechanical Watch

A mechanical watch must be wound manually (by hand).

Minute Repetition

A complication on a watch that can strike the time in hours, quarters, or seconds by means of a push piece. This complication is considered to be the most complicated of them all.

Moon Phase

An indicator that keeps track of the phases of the moon.

Deployment Clasp

A metal clasp that connects the two ends of the watchband. When the clasp is fastened, the buckle hides the deployment mechanism. Compare with the Tang Buckle

MOP or Mother Of Pearl

Material used on watch dials. Gives the surface a beautiful shimmering color. Mother-of-Pearl is an organic composite material.


A very advanced complication including two seconds hands. The other is able to move separately. It makes possible the measurement of split second times or timing simultaneous events of unequal duration.


The ring that surrounds the watch dial. The bezel is usually made of gold, gold plate or stainless steel.

Skeleton Watch

A watch in which the case and various parts of the movement are of transparent material, enabling the main parts of the watch to be seen.


Tachometer measures the speed at which the wearer has traveled over a measured distance. Converts the seconds in to kilometers per hour.


Tritium is a slightly radio-active substance used for its luminous effect on watch hands and hour markers. The radiation is so low that there is no health risk. Watches bearing tritium must be marked as such, with the letter T on the dial near 6 oclock.


Tourbillon is a watch mechanism which compensates for vertical positional errors with the help of a rotating platform. Tourbillon was invented in 1801 by Louis Breguet and is manufactured in various forms by several watch manufacturers.

Water Resistant

100 M marking on a watch does not mean that watch is water resistant up to a 100 meters, it is a code for water resistance. 100 M (10 ATM's) is suitable for swimming, and 200 M (20 ATM's) is suitable for diving.

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Watch On Watch is a limited company selling watches online (such as Rolex, Omega, Tag Heuer). Our mission is to offer the widest product range and great service. Every watch comes with all manufacturer warranties and certificates. All watches are also fully insured during transportation.

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