Montblanc caliber MB M13.21

Manually wound monopusher chronograph with column-wheel and horizontal coupling. Diameter of 29.50 mm; height of 6.40 m. Number of components 239 including 22 rubies. Power reserve of approximately 55 hours. Screw balance with a diameter of 11.40 mm; moment of inertia is 26 mgcm². Frequency of 18,000 A/h (2.5 Hz). Hairspring with Phillips terminal curve. Finished with rhodium-coated German silver plating with circular graining on both sides & hand-chamfered edges, and rhodium-coated German silver briges with “Côtes de Genève”, circular graining on both sides & hand-chamfered edges. Going-train is gold-coated, circular grained, chamfered, featuring diamond hubs on both sides.