ISO 3159 Standard
A global benchmark
The ISO 3159 standard defines the criteria that a mechanical movement must meet to be awarded the title of ‘certified chronometer’.
Developed in Geneva in 1976 by the International Organisation for Standardisation, it is now an international standard applied by a number of accredited laboratories in Switzerland, France and Germany.
A strict protocol
Each movement is tested for 15 days, in 5 positions and at 3 temperatures (8°C, 23°C, 38°C). The goal is to ensure that the precision displayed is not the result of chance, but the reflection of consistent, measurable and reproducible performance.
At the end of these tests, the movement must meet strict criteria defined by ISO 3159. The best known of these is maintaining a precision of between -4 and +6 seconds per day.
This rigorous protocol gives the chronometer title a value based on clear, objective and internationally comparable measurements.
7 criteria
Certification is based on seven criteria:
- Average daily rate: -4 to +6 seconds per day
- Average rate variation: 2 seconds per day
- Maximum daily rate variation: 5 seconds/day
- Difference between horizontal and vertical positions: -6 to +8 per day
- Largest step deviation: 10 s/day
- Step variation as a function of temperature: ±0.6 s/day°C
- Resumption of operation: ±5 s/day
An objective guarantee — This rigorous protocol confers a rare value upon the chronometer title, based on clear, objective measurements that are comparable on an international scale.