ZRC Grands Fonds 300, Serie 3 “Marine Nationale” Here at the Chrono Duo, we love rare watches and this ZRC Grandes Fonds 300, Serie 3 Marine National is no exception. Many collectors will have never heard of ZRC, let alone be aware of the superb divers watches they produced. If you have arrived here, you are one of the very few that do! So, who was/is ZRC? The company was founded in 1904 by Edmond Zuccolo and Joseph Rochet primarily producing watch chains and metal watch bracelets. They are credited for producing the first-ever extendable metal bracelet and ZRC became a world leader in their manufacture. Their expertise in metal fabrication meant the business expanded into making water-proof cases for other manufacturers dive watches; and in 1958, having been made aware of a tender to supply timepieces to the French National Navy, the firm started development of the own design, the ZRC Grands Fonds watch. They were awarded a contract to supply watches in 1960, specifically for the French Navy’s Divers within the Toulon Diving School, the Third Division of Toulon Mine Clearance Divers’ Group, and the Commando Hubert. They were also issued to the famous diver Jacque Cousteau and his team on board the Calypso. Esteemed company indeed! Dive watches were as new as Scuba diving and a big “No-No” for watches being used underwater is water ingress, particularly sea water. Rolex and many others developed the screw-down crown, Panerai their Crown Protecting half-moon guard. ZRC went one further, and developed a unique screw-down crown tailored to fit between the lug at 6 o’clock. As an extra safety measure they also designed the strap to be a close fit to the crown, ensuring the crown can only pass through the bracelet in the closed position. This feature prevents the user from wearing the watch unless the crown is fully screwed down. Finally, as a belt and braces measure the crown has a reverse screw thread, so “Righty loosey, Lefty tightly”! The ZRC Grands Fonds 300 Series 3 we have here is in great condition. The dial, hands, case, bezel and bracelet are all original and is a testament to ZRC’s build quality. The dial is showing bleed from the luminous dots creating a halo type effect around them, while the dial is showing light foxing with its centre starting to turn grey from sunlight exposure. The sword style hands with lollipop seconds hand are also showing foxing which just adds to the watches overall patina. All rather pleasing. The sharp edged lozenge shaped case (no fancy polishing here!) measures 36mm x 42mm and has minimal scratching or dents, suggesting a less stressed life. It sits on a wrist extremely comfortably. The proprietary 4-slot domed case back is in equally good nick and is embossed with the ZRC logo with Brevet S.G.D.G below. Above the logo is its serial number (6911054), suggesting this is a watch from1969, but we don't actually know. Being a Series 3, it sports the more traditional 60-click dive bezel with minute markers, rather than the simpler (but less useful) “dots” found on the series 2. It too, is in great shape, but the large triangle of lume at 12, we suspect, isn’t original. The unique expandable bracelet fits a 20cm wrist with ease and at full stretch an extra 2cm is available. The bracelet was designed to stretch so it would go over a wet-suit without having to physically adjust it, a well thought out solution. The locking clasp ensures it won’t come off the wrist and this is working as it should. Finally, the ETA 2472 movement contained within was fully serviced in January of 2025 and is working as it should. The movements anti-magnetic cover and compression disc (a device that negates the need for a helium escape valve) are also present. So, a watch designed for the most extreme of military environments, that looks like no other, with unique solutions to a diving watch’s foibles, what’s not to like!