COSC Chronometer watches

A chronometer is far more than just a watch. It stands for high precision and certified quality. The term does not refer to a watch that measures time, but rather to a precision timepiece that has undergone rigorous testing by independent institutions and has obtained an official certificate.

The best-known certification is the COSC certificate from the “Contrôle Officiel Suisse des Chronomètres”. This seal is only awarded to movements that pass an intensive testing procedure in accordance with COSC standards. Over a period of 15 days, the movement is tested in various positions and under different temperatures to simulate everyday wear. Its accuracy is checked several times a day and evaluated with precision. These tests are based on the international ISO 3159 standard, which has defined the criteria for certified chronometers for decades. It only receives its individual certificate and serial number if the movement runs with precision in everyday use and its daily deviation is between –4 and +6 seconds per day. COSC-certified watches can be recognised by the “Chronometer” designation on the dial or in the official documentation.

In addition to the COSC certification, other prestigious Swiss institutions also test and certify watchmaking standards. METAS (the Swiss Federal Institute of Metrology) awards the “Master Chronometer” title. First, it tests the movement according to ISO 3159, then it assesses the complete watch against modern standards, such as resistance to magnetic fields and water. The Timelab competence centre in Geneva certifies the craftsmanship and origin of movements with the “Poinçon de Genève”, but also conducts accuracy tests with the “Observatoire Chronométrique+”.

COSC, METAS and Timelab are among the most well-known certifications today, while other testing centres often have a regional or specialised focus. A certified watch therefore represents both timeless design and technical excellence. For watch enthusiasts, it is a reliable indicator for precision, quality and authentic horological craftsmanship.