Chronometercertified

Chronometercertified refers to mechanical or quartz timepieces that have passed independent precision and performance tests and received formal certification. The term is commonly used in the watch industry to indicate that a movement meets defined accuracy standards established by an official testing body.

Most widely recognized is the Swiss Chronometer certification administered by COSC (Contrôle Officiel Suisse des Chronomètres). COSC testing is carried out on individual movements over a series of positions and temperatures and yields quantitative measures such as mean daily rate and rate variation; results are recorded on a certificate. Certified movements are often labeled "chronometer" on dials or papers. International standards, such as ISO 3159, define technical aspects of chronometer testing for wristwatches.

Chronometer certification historically emerged from observatory trials and industrial standardization in the 20th century. In recent years manufacturers and institutes have introduced additional regimes—such as industry-specific or manufacturer-backed programs—that add criteria like magnetic resistance or testing of fully assembled watches (for example, METAS "Master Chronometer" certification).

While certification attests to a movement’s tested performance under controlled conditions, actual wrist-worn accuracy can differ because casing, regulation, and daily wear affect results. The designation remains a recognized indicator of quality and precision but is one of several factors consumers consider when evaluating timepieces.