391

The hand-wound in-house Jaeger-LeCoultre Calibre 391 employs the Duometre concept with two independent barrels and gear trains linked by a shared escapement to maintain precision during chronograph use. It features a monopusher chronograph with central seconds, a foudroyante at 6 o’clock, a 30-minute counter, moon phase, day/night indicator, and dual power reserve indicators. This 33.7 mm by 8.24 mm movement contains 482 parts and 54 jewels, running at 21,600 vibrations per hour (3 Hz) for 50 hours.