Water Resistance

Waterproof means only protected against sprinkle water, not for swimming.

Water resistant 30m means tested for 30 min. in 1m depth and 90 sec. in 20m depth. Such watches are not suited for swimming, showering etc. For swimming the watch has to have 50m/150 ft and for diving 100m = 100 meter/300 ft or more.

Screw crown and case back ensures extreme water resistance, always screw these parts tight, but not over tight to prevent seals from being squashed.

Chronograph vs. Chronometer:

Chronograph: Watch with time stopping functions, usually indicated on small sub dials.

Chronometer: Very accurate mechanical watch having passed an accuracy test at the independent Swiss Control Agency "C.O.S.C" (Contrôle Officiel Suisse de Chronomètres). The movement is tested in different positions for up to 2 weeks and it´s accuracy does not exceed - roughly said - about +/- 5 sec. per day, it gets the COSC certificate. On Quartz watches, this test does not make much sense since it's their nature not to exceed a few sec. per month in accuracy.
 

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