a-chronometer

A chronometer (from Ancient Greek χρονόμετρον) is a specific type of mechanical timepiece tested and certified to meet certain precision standards. In Switzerland, only timepieces certified by the Contrôle Officiel Suisse des Chronomètres (COSC) may use the word chronometer on them. Outside Switzerland, equivalent bodies (such as the Japan Chronometer Inspection Institute) have in the past certified timepieces to the same internationally recognised standards, although use of the term has not always been strictly controlled. https://en.wikipedia.org/wiki/Chronometer_watch