H

Hand – Moving part of the face of a watch which indicates on the dial values such as hour, minute, date etc.





Helium escape valve – Divers watches are often fitted with a HEV. Air with a higher helium component is used in diving applications conducted at great depths. Helium, having a smaller molecular size than other air elements, can move in and out of a watch casing regardless of seal. When depressurizing, either in open water or even pressurized cabin helium can become trapped inside the casing, blow out the glass/crystal and damage components. A helium escape valve allows one way movement of expanding helium to escape the casing.






Horology – The study of time and watches.









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