Friday, March 14, 2025

The eXtract: COSC Standards for Watch Accuracy

[This article is based on my X posts exploring COSC-certified watches.]

There are standards bodies for timepiece accuracy and I've been looking into them. The Swiss watch certification body, Contrôle officiel suisse des Chronomètres (COSC) certifies the accuracy of mechanical and quartz chronometers by testing each individual watch that is submitted to them by manufacturers.

COSC Mechanical Chronometer Standards

For example, to earn the Swiss COSC Chronometer certification, a mechanical (usually automatic) watch must have precision of -4/+6 seconds per day.  Rolex, Omega, Mido,Tudor, and Tissot submit the most watches for COSC certification. 

Here is a COSC-certified Mido Commander Chronometer on Amazon. At around $1300, the Mido Commander isn't cheap.  But, it's also not out of the realm of a possibility for someone determined to save and get a really accurate watch.

A Mido Commander COSC-certified chronometer (Amazon photo)

COSC Quartz Chronometer Standards

To earn a COSC certification, a quartz watch has to be accurate to + or - 0.07 seconds per day. It also has to meet standards for accuracy under various temperature and humidity conditions as outlined here on the COSC website

A good example of a COSC certified quartz watch is the Certina DS Podium. It's an attractive, accurate watch and it's available for less than $500! If you'd like to check this one out, here it is on Amazon.

Certina DS Podium Quartz COSC-certified Chronometer (Amazon Photo)

Finally, men aren't the only ones with watch bragging rights. This Certina DS Action Lady Diamonds women's watch has the COSC-certified performance brawn of a Precidrive quartz movement to back up its beauty. You can find it here on Amazon.

Certina DS Lady Diamonds

Other watch certifying bodies include the Geneva Seal, the Besançon Observatory, METAS, and the Fleurier Quality Foundation. Chopard and Vacheron Constantin certify watches via the Geneva Seal. For affordable COSC-certified chronometers, check out my post--



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