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.
- Jaeger-LeCoultre Heraion Chronograph
- Jaeger-LeCoultre Kyros Chronograph
- Jaeger-LeCoultre Odysseus Chronograph
- Jaeger-LeCoultre Master Chronograph
- IWC Porsche Design Sportivo 02 Chronograph
- IWC Porsche Design Titan Chronograph
- IWC Ref. 3739
- IWC Ingenieur Chronograph
- IWC Portofino Chronograph
- IWC Ladies Portofino Chronograph
- IWC Flieger Chronograph
- IWC SL Chronograph
- IWC GST Chronograph
- Chopard Happy Sport Chronograph