THE OFFICIAL SWISS CHRONOMETER TESTING (COSC)
The Official Swiss Chronometer Testing (COSC) is an independent Swiss body responsible for certifying the accuracy of mechanical watches and their Movements, in accordance with iSO standard 3159. Founded in 1973 under the Impulse of the watchmaking cantons (Bern, Geneva, Neuchâtel, Solothurn and Vaud), it succeeded the former cantonal testing offices. Each submitted Movement is tested individually for fifteen days, in five positions and at three temperatures, before being awarded — or not — the title of chronometer. Only Movements that have met all the criteria of the standard receive an official rate certificate.
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