The 975 is an automatic dual timezone movement made up of 230 pieces. It runs at 28800 vph, has 29 jewels, and a power reserve of 48 hours. This new movement family uses ceramic ball bearings for the rotor, increasing durability and extending the service interval. It also lacks the bidirectional winding gearing found on most earlier Jaeger-LeCoultre movements, favoring a unidirectional rotor for durability and improve power transmission. The balance spring is a new design supplied by Richemont sister company A. Lange & Söhne and is laser welded to the balance. Rather than a regulation index, the balance is adjusted by means of four screws, and the balance cock has been replaced by a screwed bridge.
There are two current versions of the basic JLC 975 movement, differing mainly in their implementation of the dual timezone function
- The JLC 975H shows the second timezone using both a 24-hour subdial and a skeleton hour hand co-axial with the main hour hand. It also supports subdial seconds.
- The JLC 975D uses only the 24-hour subdial for the second timezone and omits the seconds subdial altogether.
The 972 is similar to the 975 but adds a “Dualmatic” feature that allows the 24 hour coaxial dial to be repurposed as a minute counter using a second crown.
Jaeger-LeCoultre currently uses this calibre in 5 watches.