Who is the COSC and what do they do?
The Control Officile Suisse de Chronometers is a Swiss testing laboratory that certifies watches, or rather their movements, as “chronometers.” Each movement is individually tested over a 15-day period in different positions and temperatures, and passes only if it shows a loss of fewer than five seconds per day. Watches that have certified movements will usually be stamped with an inscription that says “Chronometer,” “Certified Chronometer,” or “Superlative Chronometer Officially Certified.
The Control Officile Suisse de Chronometers is a Swiss testing laboratory that certifies watches, or rather their movements, as “chronometers.” Each movement is individually tested over a 15-day period in different positions and temperatures, and passes only if it shows a loss of fewer than five seconds per day.
