Swiss Watch Certifications: Chronometer (COSC), METAS, and Rolex

The introduction of quartz watches was labeled a ‘crisis’ for a reason. These mass produced, inexpensive, battery-powered movements are far more accurate than their mechanical counterparts. Mechanical movements vary. They’re subject to inaccuracy via gravity, temperature, magnetic fields, etc. While mechanical imperfection is part of a watch’s charm, nobody wants an inaccurate watch. This is where watch/movement certifications come in. Some are given by independent institutions, some by government agencies, and others by the watchmakers themselves. What goes into these certifications? Let’s cover the (Swiss) basics.

Chronometer – COSC Certification

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The Contrôle Officiel Suisse des Chronomètres (COSC) is an amalgam of private institutions from the late 19th century, although it was officially founded in 1973. COSC provides ‘chronometer’ certification for Swiss movements. It’s important to note that this is a movement certification prior to encasement. Movements go through a 15-day accuracy test measured at 5 orientations (and 3 temperatures (8°C, 23°C, 38°C). If a movement stays between -6/+4 seconds per day, meeting 7 statistical variation criteria, it is deemed a COSC-certified chronometer. This is a great accuracy threshold, but a fairly narrow test. There’s more to a watch than the accuracy of its uncased movement. Regardless, COSC certification is an esteemed standard in Swiss watchmaking. 

Master Chronometer – METAS Certification

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Founded in 1862, The Swiss Federal Institute of Metrology (METAS) is a government agency parented by the Swiss Department of Justice and Police. They measure pretty much everything: radiation, acoustics, density, etc. Mechanical watch accuracy is probably their least consequential focus, but that doesn’t mean their tests aren’t stringent – quite the opposite. In tandem with Omega, METAS developed ‘Master Chronometer’ certification. Although Omega was a collaborator, this certification is not exclusive to their watches.

METAS took one look at COSC’s certification and said “that’s a good start”. Seriously – they only test watches with COSC chronometer movements. Unlike COSC, METAS requires fully-assembled watches – case and all. Not only does this closely resemble real-world conditions, it allows for water resistance and exhaustive anti-magnetism testing.

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METAS’s accuracy threshold is tighter than COSC’s at -0/+5 seconds per day. Encased watches are tested at 6 different orientations (similar to COSC), as well as different levels of power (between 33% and 100%). The power reserve itself is also tested – making sure it aligns with or exceeds the brand’s duration claims. To test anti-magnetism, METAS exposes a movement to 15,000 gauss: in and out of its case. Throughout all testing, a watch must remain within METAS’s -0/+5 threshold.  They even test water resistance, even though as Ripley Sellers says, “it has nothing to do with the movement or performance”. This is what makes METAS Master Chronometer certification so highly regarded; watches and movements are truly tested. A Master Chronometer is more than an accurate movement; it’s a categorically dependable watch. 

Superlative Chronometer – Rolex Certification

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Rolex’s ‘Superlative Chronometer’ certification, designated on the Rolex Daytona dial pictured above, was introduced in the 1950’s. This is Rolex's in-house certification: exclusive to their own watches. In 2015, Rolex reinforced the stringency of this certification, requiring it for every watch in their lineup. Like METAS certification, Rolex tests fully-encased, COSC-certified movements. To be deemed a Superlative Chronometer, a watch must be accurate within -2/+2 seconds per day. Rolex tests proper functionality of the self-winding rotor, accuracy of the listed power reserve, and water resistance of at least 100 meters (higher for dive watches).

Rolex’s in-house certification is not the only of its kind, but it’s certainly the most well-known. It takes a certain level of prestige to offer “superlative” certification of your own product. It’s very in line with Rolex’s brand. They hold themselves to an extremely high standard – above and beyond other watchmakers. In the same way that Rolex follows their own historic design cues, they follow their own standards for certification. It sends the message “we know what makes a great watch” – and nobody has any reason to deny it. 

Final Thoughts

High-end Swiss watches are expensive for a reason. Inside and out, no detail is spared. A chronometer, be it ‘Master’, ‘Superlative’, or neither, is going to provide accurate timekeeping. METAS and Rolex go above and beyond with their additional testing. These certifications are incredible displays of quality, designating not just watches, but heirlooms.