More watch companies are coming up with their own certifications, accompanied by their own set of standards – but there are some long-standing stamps of excellence that will be familiar to any fan of horology. One of these is COSC certification.

Short for Contrôle Officiel Suisse des Chronomètres, or the Official Swiss Chronometer Testing Institute, COSC tests and certifies chronometers, or precision watches. A non-profit organization, COSC tests some 1.8 million movements annually, or some 6 per cent of watch production in Switzerland. Rolex and Omega together account for over half of the watches tested.

Given its scale, COSC’s tests are automated, and cover only movements, rather than whole watches. That being said, COSC certification is often seen as an upgrade. Tudor, for instance, introduced the second-generation Black Bay diver’s watch at Baselworld 2016, with the most substantive change being a new in-house movement that is COSC-certified.