METAS is not a trademark: it is the Swiss Federal Institute of Metrology, a state institution based in Bern. The difference from COSC is structural, not merely a matter of tolerance. COSC tests the raw movement before case assembly. METAS certifies the finished watch, with the case closed, crown screwed down, and crystal installed. This changes everything, because a caliber that runs well on the bench can behave differently once cased.
METAS tolerances are tighter: 0 to +5 seconds per day, versus COSC's -4/+6. The asymmetry is not an error: METAS allows only gain, never loss, reflecting a philosophy of precise and deliberate regulation. The magnetic resistance test is set at 15,000 gauss, a threshold that far exceeds the magnets found in daily life, including bag closures and some speakers. For comparison, a 15,000 gauss magnetic field is comparable to that of certain industrial machinery.
The complete protocol involves eight tests conducted over ten days: accuracy in six positions, two charge reserve levels, two temperatures, magnetic resistance before and after casing, water resistance verified against declared depth. This assembled-watch testing procedure is what distinguishes METAS from a simple certified chronometer.
The certification was introduced in 2015 by Omega with the Globemaster, which housed the 8900 caliber. Tudor adopted the same standard on its in-house movements, recognizable by the letter U in the caliber code: MT5601-U, MT5602-U, MT5612-U. Not all Tudor models carry the U, meaning the catalog contains both COSC-only and dual-certified movements. The distinction is technical and must be read in the caliber code, not in the watch's commercial name.
From my bench, I've seen clients confuse METAS with an Omega certification because Omega brought it to prominence. METAS is an independent third party: it certifies anyone whose movement passes the tests. I don't know how many other manufacturers are considering adoption, but the trend toward certifying the complete watch rather than just the movement seems here to stay.