Buren Calibre 82
Developed in the late 1960's, Calibre 82 was intended to compete with the high-beat movements coming from Zenith, Girard Perregaux, and others. But Buren was sold to Hamilton before development finished and just 250 movements were produced. It was tested in 1970, receiving one of the highest chronometer ratings ever recorded It achieved a Chronometer Index of 4.4, making it the most accurate mechanical movement ever certified! It achieved a variance of between +15 and +60 seconds per 30 days, far exceeding the test parameters.
The Calibre 82 movements were sold along with Buren in 1971 and remained unused until a run of 238 “Calibre 82” watches was produced in 1998 and 1999.