Glossary

Contrôle Officiel Suisse des Chronomètres, is an independent Swiss organization responsible for certifying the performance and accuracy of mechanical watches through a series of tests on watch movements. It is considered one of the highest standards in the watch industry for measuring the performance and accuracy of watches.

The watch movement undergoes a series of rigorous tests and measurements under various temperature conditions over a specified period, typically up to 15 days. These tests evaluate the performance and accuracy of the watch.

To achieve the COSC certification, the average daily rate of the watch must fall within a specific range of -4 to +6 seconds per day. This means that the watch should not deviate more than -4 to +6 seconds from the exact time over a 24-hour period. Additionally, the movement must meet specific criteria for accuracy, stability, and reliability.