H. Moser’s once-vaunted perpetual calendar is reengineered for the real world.

When the results of the Grand Prix d’Horlogerie de Genève were announced in 2006, most of the winners were well-established brands such as Breguet and Patek Philippe. But the award for best complicated watch went to newcomer H. Moser & Cie.—a briefly defunct Swiss German marque revived only the previous year—for a completely understated perpetual calendar engineered in collaboration with the master Swiss watchmaker Andre…