Blancpain Fifty Fathoms

Why the first Fifty Fathoms was built the way it was

Blancpain dates the Fifty Fathoms to 1953. The design came from two directions: Jean-Jacques Fiechter, who led the company and was a keen diver, and Captain Robert Maloubier and Lieutenant Claude Riffaud of the French combat divers, who had tested watches on the market and found them small, hard to read underwater, and prone to leaking. The brand's own history describes the result as large, with a white-on-black dial and luminous hands.

Several features came from Fiechter's design. The crown was double-sealed, the rotating bezel had a locking mechanism to stop accidental movement, and the screw-on caseback used an O-ring in a channel with a metal ring to keep it aligned. The movement was automatic to limit crown use, and an inner soft-iron case shielded it from magnetism. The name comes from Shakespeare's The Tempest, and fifty fathoms was then thought to be about the deepest a diver would go.

The modern line: Automatique, Bathyscaphe and the movements

The Bathyscaphe appeared around 1956 as a smaller alternative for everyday wear, and Blancpain revived it in 2013 for the Fifty Fathoms' sixtieth anniversary. The Automatique is the broader, more recognizable Fifty Fathoms, with a domed sapphire bezel. Its 2007 generation used a 45 mm case, and regular-production 42 mm versions followed in 2024. Both sizes use the same in-house caliber 1315.

Caliber 1315 is an automatic with a 120-hour reserve from three mainspring barrels connected in series, running at 4 Hz with 35 jewels. It was designed as a robust sports movement rather than a copy of a vintage caliber, and modern examples use a silicon balance spring. The 38 mm Bathyscaphe uses the 1150 movement, which Blancpain lists with a 100-hour reserve. Check the movement before you plan a service, because the two calibers are not interchangeable.

Servicing a dive watch with a long reserve

A Fifty Fathoms service should cover the movement, the crown and its seals, the caseback gasket and a pressure test at the end. The three-barrel layout of the 1315 means the barrels and their springs need careful attention, and a watchmaker who has only worked on single-barrel movements should be honest about that. Ask how the shop will handle the reserve and the time-setting, since the longer power reserve makes those checks more involved.

For a watch under warranty, Blancpain's service network is the lowest-risk choice, because factory work returns the watch with original parts and a clear record. Out of warranty, an independent who regularly services Swiss automatic sports watches can do a sound job, provided they open the case in the right order and use the correct tools for the bezel and caseback. Bezel inserts, lume and gaskets are the usual maintenance items, so ask for a parts list before you approve the quote.

Buying a pre-owned Fifty Fathoms

Start with the reference, the case size and the movement, because the Automatique and Bathyscaphe lines and their generations differ in more than the dial. Check the bezel action, looking for play, grittiness or a click that does not seat. Examine the bezel insert for fading or chips, and look at the luminous material on the hands and markers. Dive watches are sometimes sold with replaced inserts, so ask for the exact part history.

Ask for the caseback to be opened or for clear photographs of the movement and the seal, and insist on a pressure test before you pay. Vintage examples may have a moisture indicator disc at six o'clock, which turned from blue to red when water got in. A replaced or missing disc is not a dealbreaker, but it changes the watch's originality and should be reflected in the price.

Bezel inserts on well-used examples are often replaced, so ask whether the insert is original to the watch. Ceramic inserts resist fading but can chip at the edges, and the printed scale and lume wear on any insert over time. A replacement insert is not a defect in itself, but it should be listed in the service record and reflected in the price.

Care, originality and copies

The Fifty Fathoms is copied often, and the copies usually get the bezel, the dial text or the caseback wrong. Check the reference against the papers, and be wary of a watch that comes without a box, papers or a serial number. A genuine piece should match in every detail, including the dial printing and the proportions of the hands, when compared with a known reference.

Rubber straps age quickly in sun and salt water, so replace them before they crack at the lugs. Keep the bracelet and the original strap together, and ask the shop to list any non-original parts. A dive watch that has been polished too often loses its sharp bezel edges and the crispness that makes the design work, so avoid cases that have been heavily refinished.

After a day in salt water, rinse the case and any bracelet in fresh water and dry them fully before storing the watch. Salt that dries under a bezel or in the bracelet joints can work into the moving parts. Ask the shop to check the bezel action at the next service, since grit trapped there is a common cause of stiffness that owners mistake for a movement fault.

What to check on a Blancpain Fifty Fathoms

• Experience with dive watch seals, including a pressure test after every service
• Confirmation of whether your watch uses the 1315 or the 1150 before work begins
• A pre-purchase check of the bezel action, insert condition and caseback

Common questions