Jaeger-LeCoultre caliber 391

The Jaeger-LeCoultre Calibre 391 is a hand-wound chronograph movement developed and manufactured entirely in-house. It is based on the Duometre concept introduced in 2007, featuring two independent barrels and gear trains—one dedicated to timekeeping, the other to complications—connected by a shared escapement. This architecture ensures high precision even during chronograph operation. Calibre 391 integrates a monopusher chronograph with central seconds and a foudroyante (jumping seconds) at 6 o’clock, along with a 30-minute counter at 3 o’clock. Additional functions include a moon phase display, a day/night indicator, and dual power reserve indicators. The movement runs at a frequency of 21,600 vibrations per hour (3 Hz), has a power reserve of approximately 50 hours, and comprises 482 components, including 54 jewels. It measures 33.7 mm in diameter and 8.24 mm in height.