In watchmaking, certification is not a single word: it's a layered system of bodies, protocols, and standards that overlap without necessarily being equivalent. Understanding the differences matters more than any label on the dial.
The mandatory starting point is COSC, Contrôle Officiel Suisse des Chronomètres, founded in 1973. It certifies movements—not complete watches—by testing daily rate variation for 16 consecutive days in five positions and three temperatures. The allowed tolerance is between -4 and +6 seconds per day. It's a serious standard, but it concerns the raw caliber: everything that happens after casing, oiling, and final adjustment falls outside the certificate. This is the historical limit of COSC that many sellers don't mention.
The more structured answer came in 2015 with the Master Chronometer METAS, developed by Omega together with the Swiss Federal Institute of Metrology. Here the complete, cased watch is certified. Requirements include precision between 0 and +5 seconds per day, magnetic resistance up to 15,000 gauss, and water resistance verified after assembly. The Dual Metric Technology introduced by Omega for two-hand calibers adds continuous acoustic analysis over 25 days: sensors record temperature, pressure, position, and magnetic fields while the movement operates. It's methodologically more rigorous than classical COSC.
The Poinçon de Genève operates on a different plane: it measures not just precision, but also the quality of finishing. To obtain it, the watch must be assembled and regulated in the Canton of Geneva, surfaces must meet precise polishing criteria, and the finished movement must pass chronometric tests. It's the only certification that combines precision metrics with aesthetic metrics of the movement.
Qualité Fleurier by Chopard and Minerva Laboratory Test 500H are instead internal manufacture standards: rigorous within the company context, but lacking an independent third party. The same applies to the Elaboré grade of Sellita calibers, which indicates three-position regulation without external certification.
The ISO 6425 standard governs a separate territory: suitability for diving. It requires that sealing tests be conducted at 125% of the stated pressure. It says nothing about chronometric precision.
Finally, Swiss Made and Swiss Crafted: the first requires that at least 60% of the movement's value be Swiss; the second is a more restrictive voluntary designation, adopted by maisons that produce virtually everything in Switzerland, components included. They don't certify precision; they certify origin.