A unit of pressure for standard atmospheric pressure at sea level. One Atmosphere is the pressure of 1kg/cm2 and corresponds to 10 meters of depth. An ATM is displayed as a value such as 5ATM which equals 50 Metres.
Also known as a self-winding watch. An automatic watch is a mechanical watch where the mainspring is wound automatically by the nature of motion on the wearer’s wrist.
The bezel is a grooved ring holding the cover of a watch face in position. They can be fixed or rotational.
A watch that features an additional stopwatch function, usually activated by a set of pushers (one to stop, and one to reset) either side of the crown.
A knob on the side of the watch case that is used to adjust the time and date. On a non-automatic mechanical watch, the crown is used to wind the mainspring to keep the watch running.
End of life (EOL) is a useful feature. The seconds hand "jumps" every 2 or 4 seconds to indicate low power state, meaning the battery will need replacing soon.
A GMT watch has the ability to track two time zones at once.
Guilloche is a complicated mechanical engraving technique used on watch dials.
A mechanical watch that doesn’t automatically wind. Hand wound watches require the crown to be manually turned to wind the mainspring.
Found in professional dive watches, used mostly by commercial divers. Divers often spend prolonged hours in diving bells under great pressure. A Helium Escape Valve prevents any damage to the watch when returning to normal pressure.
The markings on the dial of a watch used to represent the hours, in place or alongside numerals.
Synthetic rubies or sapphires used as bearings at the heaviest points of wear in a watch movement. They are used in order to reduce friction between moving parts and increase the lifespan of the movement.
Luminescence is the glow given off by watch numerals, indices and hands that have been coated with a photoluminescent material.
A Moon phase watch is a small-scale recreation of the different phases of the Moon displayed in an aperture on the dial.
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, black, pink and more.
Running time in excess of the normal time between two consecutive windings. In an ordinary watch, the power reserve usually provides for 10 to 16 hours running.
Physical Vapour Deposition is a coating of titanium nitrate which is applied to a watch, it is then covered by a coating of another colour to achieve a high quality finish.
A quartz watch is a battery powered watch. They are far more accurate than a manually wound watch, and also much less expensive.
A watch in which the case is made from transparent material, allowing visibility of the watch’s movement.
A sub dial is an auxiliary dial on the face of the watch. This can be used for various functions including the seconds hand and chronograph functions.
A tachymeter measures speed over a specified distance.
A tourbillion is an escapement that is meant to counter the effects of gravity on a watch movement. The balance wheel and escapement are mounted on a rotating cage, allowing them to rotate freely and avoid any errors caused by gravity.