Worn & Wound
The COSC Introduces the New Excellence Chronometer Certification
The Contrôle Officiel Suisse des Chronomètres (COSC, the body responsible for certifying watch movements as Swiss chronometers) has just announced a new chronometry standard that will be rolled out over the course of 2026. The news comes at a time when the COSC has some competition for timekeeping certifications, most notably the METAS certification (which first requires a watch movement to be COSC certified) used by Omega and Tudor, as well as other certifications provided by the brands themselves. The new COSC certification is being framed as an additional level of certification that will accompany the familiar “Certified Chronometer” tag that is seen on the dials and paperwork of millions (literally) of watches that have been put through the COSC paces over the years. The new “Excellence Chronomenter” certification provides an additional layer of guarantee of reliability that goes beyond simple accuracy. As a refresher, COSC certification certifies the movement is working at an optimal level, not a fully cased watch. To achieve a Certified Chronometer certification, a movement must show average accuracy of -4 to +6 seconds per day over a 15 day period, tested across 5 positions and 3 temperatures. The Excellence Chronometer certification tightens the accuracy threshold from a spread of 10 seconds in total to 6 (-2 to +4 seconds per day). It also adds metrics for magnetic resistance and power reserve verification in fully cased watches. According to the COS...
