Historical
ISO 3159:1976
Timekeeping instruments -- Wrist-chronometers with spring balance oscillator
Lays down the definition of the term "chronometer", describing the categoeries, the test programme and the acceptable minimum requirements for wrist-chronometers. Wristwatches using a tuning fork oscillator are subjected to these tests pending the availability of separate standards.
International Organization for Standardization [iso]