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Calibre 631 was a quartz watch movement with a mechanical chronograph developed by Jaeger-LeCoultre and also used by IWC.
Introduced in 1987, Calibre 631 was the second member in the Jaeger-LeCoultre Mechaquartz family after Calibre 630. It was a complicated movement, with 25 jewels and 233 components.
There are two motors in the calibre
- One powers the main timekeeping hands at a frequency of 1 Hz
- A second powers the mechanical chronograph at 4 Hz
Since the chronograph is mechanical, it has the same feel as a conventional chronograph movement, including mechanical zero reset. Yet the Mechaquartz was much more compact than a conventional automatic chronograph movement.
Note There is conflicting information on the quartz frequency, with some sources claiming dual 1 KHz and 4 KHz crystals and others claiming 32 KHz.
Calibre 631 was widely used in chronograph watches in the 1980's and 1990's.
- Quartz movement with mechanical chronograph
- Hour, minute hands
- Small seconds at 6 00
- Chronograph with 30 minute and 12 hour subdials at 9 00 and 3 00, respectively
- H 3.8 mm
- D 23.3 mm
- 25 jewels
- 233 components
- Frequency 32 KHz