News 
Since 1973, the Official Swiss Chronometer Testing Authority (COSC) has been the independent custodian of precision. It has accompanied the rise of Swiss Made by certifying millions of movements and helping to establish our nation as the global benchmark for watchmaking excellence. On the occasion of the 50th anniversary of the ISO 3159 standard, the COSC is beginning a new chapter and looking to the future.
The life of mechanical watches has evolved over the past half-century due to various factors such as increased exposure to magnetic fields, extended power reserves, new materials and intensive use. To keep pace with these changes, the institution is introducing an additional level of certification, “Excellence Chronometer Certified”, designed as a complementary extension of the current “Certified Chronometer” standard.
Twenty days of testing
For 15 days, the movements are tested according to the seven criteria of the ISO 3159 standard. Once certified as chronometers, they return to the manufacturer to be cased up. The complete watches then undergo five additional days of evaluation. Using a robot capable of simulating average real-life wear, the timepiece’s precision is tested in semi-dynamic conditions for 24 hours. This simulation is followed by a measurement in which the rate deviation must be between -2 and +4 seconds per day. The timepiece must then continue to perform well when subjected to a magnetic field of 200 Gauss. Finally, its power reserve is checked to corroborate the figures announced by the watchmaker. As always, 100% of certified watches are tested, as the COSC does not use sampling.
Gradual ramp-up
Since the start of 2026, the COSC has been integrating new technologies and upgrading its equipment to measure all criteria for the future label. March brings the first pilot tests conducted to validate the procedures, followed in April by the global unveiling at Watches and Wonders as part of the projects showcased in the LAB: a space dedicated to innovation and new technologies. From October 2026, brands will be able to fully enter the new process and the first watches certified according to these redefined standards will begin to arrive on the market.
March 12, 2026