Watch SafeHorology glossaryDefined term / superlative-chronometer
Superlative Chronometer
Rolex's in-house certification, applied after casing, that tightens the COSC chronometer standard to a stated accuracy of plus or minus two seconds per day.
Authentication note
Why this detail matters.
The phrase appears as dial text on qualifying models, so its presence, wording, and print quality must match the reference and era. Counterfeit dials frequently misspace or misprint these two long words, making them a practical magnification check. The certification also implies the cased watch should time within tight tolerances, which a timing machine verifies directly.