Horology glossaryDefined term / chronometer-certification
Chronometer Certification
An independent accuracy certification, most commonly from COSC, awarded to individual movements that pass a multi-position, multi-temperature timing test.
Authentication note
Why this detail matters.
Chronometer certification applies to the movement, not the finished watch, and is usually marked on the movement or dial, for example as "Chronometer" or "Officially Certified." A watch claiming chronometer status without the corresponding marking, or with timing performance far outside chronometer tolerance, is inconsistent with a genuine certified example.