What Is An Officially Certified Chronometre?

If you are a luxury watch enthusiast then you will no doubt be familiar with the term Officially Certified Chronometre. But what does it actually mean? And who’s giving this certification? Read on to learn more about one of the most well-respected certifications in the Swiss watch industry.

An Explanation of the COSC Chronometer Certification
The Contrôle Officiel Suisse des Chronomètres or the COSC as its more commonly known is a not-for-profit organization that was founded in 1973. It is the Official Swiss Chronometer Testing Institute and was established by five watch-making cantons (Bern, Geneva, Neuchâtel, Solothurn and Vaud) as well as the Federation of the Swiss Watch Industry.

It encompasses the laboratories that had been established independently of each other from the late 19th century onwards and today is the only organization in the world that decides if a watch is a chronometer or not. The COSC differs in one important respect from all previous watch testing institutions and observatories. It is strictly non-competitive. There are no points awarded or any prizes. There are no degrees of success or honorable mentions.

The watches either pass or fail.

Defining A Chronometre
Before I go any further it may be helpful here to define what a chronometer actually is, as it is often mistaken with chronographs and chronoscopes. A chronometer is a high-precision watch capable of displaying seconds and housing a movement that has been tested over several days, in different positions and at different temperatures, by an official neutral body (the COSC).

Earning The Title
To earn chronometer certification, a movement must not only be made from the highest-quality components, but also the object of special care on the part of the finest watchmakers and timers during assembly. It is important to note here that that the fine regulation and chronometer characteristics of a watch can be destroyed in seconds by a rough and inexperienced hand.

Testing criteria is based on ISO 3159 which provides the definition of a wrist-chronometer with spring balance oscillator. Only movements which meet the precision criteria established under ISO 3159 are granted an official chronometer certificate.

Each uncased movement is individually tested for fifteen days, in five positions, at three different temperatures. The movements are fitted with a seconds hand and the automatic winding mechanisms are disengaged for the tests.

Measurements are made daily with the aid of cameras. Based on these measurements, seven eliminatory criteria are calculated, the minimal of which must all be met.

The Final Word
To give a bit of perspective on the value of COSC certification over 1 million official chronometer certificates are delivered each year, which represents only 3% of the Swiss watch production. This proportion truly underscores the exceptional nature of a chronometer and certainly makes it a key factor for consideration when purchasing your next luxury watch.

For more information check out the official COSC website:

Tags: calibre 89, certified, Chronometre, COSC, diving watch, Dual Time, luxury, Omega, patek philippe, rolex, Seamaster, submariner, Watch

Category: Recommended Reading