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.