After granting its official approval to the first Grands Fonds 300^® in 1960, the French Navy explained to the designers that the crown at 3 o’clock posed a problem as it was too vulnerable during underwater manipulations. It asked ZRC^® to “find a solution” to protect the crown without impeding wrist movement, and above all, to ensure it could not open under water. The team set to work and developed the famous crown at 6 o’clock, connected to the case using an exclusive system consisting of a canon cut from a single block, making the Grands Fonds 300^® the first and only watch to be equipped with a 100% monobloc case. Furthermore, the case is machined in a particular type of steel reinforced with molybdenum that is completely antimagnetic (an absolute necessity for Mine Clearance Divers’ Group).

ZRC 1970

ZRC^® developed an exclusive retractable lug specific to the inter-horn space, which only allows the crown to pass through or the bracelet to rotate in the closed position, making submerging the watch impossible if the crown is not fully screwed down. The bracelet is also original by virtue of its two extendable links, allowing the watch to be worn over a diving suit with no further adjustments. The ultra-luminescent Magnum hands ensure perfect legibility underwater. A revolutionary watch in many ways, the ZRC Grands Fonds^® was issued to the Paris fire service and the French waterskiing team. But it was above all the watch of the French Navy (Toulon diving school, third division of Toulon Mine Clearance Divers’ Group, the Commando Hubert) as well as the Italian Navy. As a watch designed by divers for divers, it was also adopted by non-military units supported by the French Navy, including the famous Calypso of Commander Cousteau, which took the watch around the world and firmly established its reputation.