Watch glossary: G, H, I, J, K.
GENEVA SEAL, see poinçon de Geneve.
GLASS, see also crystal
Thin plate of glass or transparent synthetic material, for protecting the dial of the watch.
GLUCYDUR
Bronze and beryllium alloy used for high-quality balances. This alloy assures high elasticity and hardness values; it is non-magnetic, rustproof and has a very reduced dilatation coefficient, which makes the balance very stable and assures high accuracy of the movement.
GMT
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 a.m. or p.m. in that zone).
GONG
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 resulting 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).
GUILLOCHE
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.
HAMMER
Steel or brass element used in movements provided with a repeater or alarm sonnerie. It strikes a gong or bell (s).
HAND
Indicator for the analogue visualization of 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.
HARDLEX CRYSTAL
is Seiko's trademarked name for a hardened mineral crystal.
HEART-PIECE
Heart-shaped corn, generally used to realign the hands of chronograph counters.
HELIUM VALVE
Valve inserted in the case of some professional diving watches to discharge the helium contained in the air mixture inhaled by divers.
HEXALITE
An artificial glass made of a plastic resin. Back in the 1960's, many watches used either mineral glass or acrylic crystals. These are not difficult to scratch, but very inexpensive to replace. Now though, most all luxury watches use the highly scratch resistant synthetic sapphire crystals, there are some styles/brands that use the Hesalite (a name brand of fine acrylic crystal). The reason for this is directly related to the watch's certification for use in space or in high stress/impact situations. While sapphire crystals are less prone to scratching, they can be shattered. When shattered, they break into tiny fragments that would be hazardous in some environments. So the Hesalite crystal is maintained on some specific models as a safety feature.
HUNTER CALIBER
A caliber characterized by the seconds hand fitted on an axis perpendicular to the one of the winding stem.
INCABLOC, see shockproof.
JEWEL
Precious stone used in movements as a bearing surface. Generally speaking, the steel 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).
JUMPING HOUR
Feature concerning the digital display of time in a window. The indication changes almost instantaneously at every hour.
KINETIC
Refers to the Seiko line of Kinetic watches. This innovative technology has a quartz movement that does not use a battery. Movement of the wrist charges a very efficient capacitor which powers the quartz movement. Once the capacitor is fully charged, men's models will store energy for 7-14 days without being worn. Ladies models store energy for 3-7 days. Of course, if the watch is worn every day the capacitor is continually recharged. The watch alerts the owner to a low capacitor charge when the seconds hand starts to move in two second intervals. Some of Seiko's Kinetic Watches have See-Thru CaseBacks, that use a clear, Hardlex crystal watch back to enable the wearer to view the kinetic movement.
KINETIC AUTO RELAY
A Seiko Kinetic Auto Relay watch is powered by human movement, however when it senses inactivity for three days, it puts itself into suspended animation to conserve energy. It can be re-activated with a few shakes of the wrist. It automatically resets itself to the exact time after to up to four years of dormancy.
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