Behind the scenes of certification
Very specific rules
Quality, rigor and impartiality are the very foundations of the COSC label.
Our certificate is the result of a true test of excellence, guaranteeing that every second generated by Swiss movements meets the industry's most demanding standards.
Four types of timekeeping instruments
The COSC mainly certifies mechanical wristwatches, but also pocket watches, fixed-time devices and quartz wristwatches.
To obtain “Certified Chronometer” certification, wristwatch movements must meet the criteria set out in ISO 3159, which define a wristwatch with a balance-spring oscillator.
Movements in other categories, including quartz watches, are based on in-house specifications inspired by ISO 3159, but adapted to the specific features of each instrument.
Each movement undergoes the most stringent tests, integrating temperature and position variations, over 12 to 20 days, depending on its type, in order to ensure optimal precision.
The stages of certification
Our 7 criteria for certification
To qualify as a Certified Chronometer, movements must meet 7 criteria. At the end of all the tests, a calculation is performed to verify that these criteria have been met:
Average daily rate
Rate variation as a function of temperature
Rate resumption
Greatest difference in rates
Difference between rates in horizontal and vertical positions of the watch
Greatest variation in rates
Mean rate variation
SAS Accreditation
The COSC has been accredited for twenty years as a calibration laboratory with the Swiss Accreditation Service, SAS. SAS accreditation formally recognizes COSC's technical and organizational competence to perform a defined service.
The reliability of an independent label
Founded on principles of fairness and transparency, the COSC pays tribute to the genius of Swiss watchmaking by measuring, certifying and celebrating precision.
SAS accreditation is a guarantee of the quality, consistency and neutrality of the measurements performed. The COSC's independence is a key factor in its rigor and credibility.
The certification
FAQ
What does the COSC stand for?
The COSC, or the Official Swiss Chronometer Testing Authority is a non-profit public interest association founded in 1973. Its mission is to certify the precision of Swiss watches as chronometers. The COSC encompasses the laboratories that were originally created independently of each other as early as the late 19th century. Today, it operates across three monitoring sites in French-speaking Switzerland, in Bienne, Le Locle and Saint-Imier, and is coordinated by a management team based in La Chaux-de-Fonds.
What does the COSC represent for a watch?
The COSC is a guarantor of high precision and quality for a watch. When a watch is certified by the COSC, it receives the official designation of “chronometer,” meaning that it has passed a series of rigorous tests to verify its precision. These tests are based on strict criteria defined by the ISO 3159 standard for mechanical watches, and internal requirements for quartz watches. The COSC certification is a guarantor of expertise and reliability, enabling manufacturers to stand out in the market by offering added value to their products.
What is the COSC certification?
The ISO 3159 standard is an international reference that governs methods for testing and evaluating the precision of chronometers. It seeks to establish uniform criteria for the testing and evaluation of timekeeping devices, whether they be watches, clocks or other chronometric instruments used in specific applications such as sports competitions, scientific instruments or military equipment. The ISO 3159 standard plays a key role in standardizing the methods used to ensure the precision, reliability and durability of chronometers.
Guarantor of precision: Users can have the assurance that chronometers tested in accordance with the ISO 3159 standard meet strict precision criteria, and that the results of the time measured are reliable.
Interchangeability: The uniform application of this standard throughout the world makes it possible for time measurement instruments to adapt to international measurement systems, offering greater flexibility for users.
Performance optimization: By establishing clear criteria for chronometer performance, the standard encourages manufacturers to constantly improve the quality of their products.
Certification and international recognition: Those chronometers that meet the requirements of ISO 3159 can be certified, enabling manufacturers to gain an international recognition for the precision and reliability of their products.
The ISO 3159 standard represents a major step forward in the management of chronometer accuracy and performance. By providing a framework for rigorous, standardized testing, it ensures that these instruments meet strict reliability criteria, which is essential in fields where time is critically measured. By ensuring greater reliability, this standard strengthens the confidence of users - whether industry professionals, top sportsmen and women, researchers or consumers - in the accuracy of the chronometers they use.