Chronometer: certified precision timepiece
A chronometer is a precision timepiece. When assessing certified wristwatches, the designation concerns timekeeping tested against specified requirements. Longines explains that a neutral body tests the movement and issues a certificate. Distinguish the term from chronograph, which describes an elapsed-time measuring function.
What does the certificate document?
Check the testing organisation, the identifying number and what was actually tested. Longines names COSC and Timelab as examples of independent laboratories. The same manufacturer also describes a specific case in which the complete watch head, rather than just the movement, was submitted to Timelab. That example is not a rule for every watch from the brand.
MASTER CHRONOMETER is a separate certification under METAS requirements. METAS lists precision under various influences, power reserve and water resistance among its tests. These requirements must not automatically be attributed to every older watch with chronometer on its dial. This overview of the schemes was checked on 1 November 2026.
An older watch needs current assessment
A historical certificate records a particular test. When buying second-hand, also investigate current timekeeping, condition and service history. A certificate alone does not replace a current functional check. Ask for documentation identifiable with the individual watch.
As a practical example, compare identifying numbers on a loose certificate and a watch from the same brand rather than assuming they belong together. Retain papers as part of the ownership history, and distinguish documentary information from your own observations in a condition report.
Next step: Browse OBA's wristwatches and compare the stated condition and documentation for each example.
Sources: Longines on chronometer certification and METAS on watch certification.
