Cal. PF331 was the first fully in-house watch movement for Parmigiani Fleurier. Introduced in 2001, it has become the base for a range of automatic movements from the company. It features two mainspring barrels in series for 50 hours of power reserve. It has uni-directional automatic winding in the clockwise direction.
Viewed from the back with the crown at 9:00, the balance is placed at 8:00 on a clockwise cock. The central winding rotor is held with three screws and has seven ball bearings visible.
Hermès P1928 and H1837
In 2006, Hermès invested in 25% ownership of Vaucher Manufacture, along with Parmigiani. The company initially produced a version of Cal. PF331 for Hermès called P1928.
In 2017, these were updated with distinctive bridges and other customization and renamed Cal. H1837. Both Cal. PF331 and Cal. PF332 were used by Hermès, both named Cal. H1837.