Dual crown

The dual crown is a constructive solution born in the submarine industry of the 1950s and 1960s, when case manufacturers — particularly EPSA (Ervin Piquerez SA) and Sherpa Watches — sought a way to separate distinct functions without compromising water resistance. The principle is simple: two independent crowns, each with a precise task, mounted at different positions on the case.

In the context of vintage divers, the system is called a compressor: one crown controls the rotating inner bezel (minute scale or decompression times), the other manages winding and movement regulation. Both are threaded and often shielded by a guard. The operational advantage is real: the diver can update the reference time on the bezel without touching the regulating crown, reducing the risk of accidentally moving the hands at depth. The Longines Legend Diver maintains this original architecture today with appreciable technical fidelity. Models inspired by the compressor style, such as certain Ultradive models with crowns at 2 o'clock and 4 o'clock, descend directly from that tradition.

Outside of diving, the dual crown appears in different contexts. On the Rolex Land-Dweller, one of the crowns is associated with the patented dual-wheel escapement, which represents one of the first series industrializations of that escapement architecture. On certain split-seconds chronographs, the coaxial crown with integrated pusher manages the dual-hand function. In all cases, the dual crown signals a design choice: it was preferred to multiply external access points rather than overload a single crown with multiple functions through pull positions.

From the workbench, a detail that magazines often overlook: the water resistance of a dual-crown system depends almost always on the quality of the crown tubes, not just the seals. On vintage pieces, silver or brass tubes oxidize internally and compromise the thread before the seal even fails. When I examine a vintage diver with a dual crown, I always check the internal condition of the tubes before any pressure testing.