Blancpain can boast a long history of providing divers’ watches for military units since its introduction of the original Fifty Fathoms in 1953. By the mid-1960s, Blancpain was producing a version of that seminal timepiece to the elite combat swimmers (“Kampfschwimmers”) of the German Navy, one notable for the use of a red-and-yellow “No Radiations” logo on its dial. The emblem indicated that the watch’s luminescent details were not composed of radium, a radioactive material that had previously been used regularly in watchmaking but by the early ’60s had been declared harmful.

The geometric hour markers and red-and-yellow logo are hallmarks of the original model.

This Fifty Fathoms RPG-1, or so-called “BUND No-Rad” model from 1963 (“BUND” referred to the German “Bundeswehr,” or armed forces), provides the inspiration for the new Tribute to Fifty Fathoms No-Rad Limited Edition. Housed in a 40.3-mm-diameter polished steel case, a size reserved exclusively by Blancpain for its Fifty Fathoms limited editions, the watch replicates many of its vintage forebear’s recognizable elements. Chief among them is the aforementioned colorful disk above 6 o’clock, whose red segments on a yellow background was designed as visual shorthand to assure the watch’s users — military as well as civilian — that the timepiece was radiation-free and not hazardous to wear for long periods as were its radium-treated predecessors.

The beige faux-vintage lume glows bright green in the dark.

Other details on the the matte black dial hearken to the 1960s ancestors, like the geometrical hour-markers, an assortment of traditional round dots, rectangles, and a diamond-shaped marker at 12 o’clock. The chapter ring, hands and dive scale on the unidirectional rotating bezel are all coated with a beige-orange Super-LumiNova (also referred to, ironically, as “old radium” colored) that replicates the look of a dial that has acquire the patina of time. The 3 o’clock date window, in a white frame, echoes the one on the 1960s’ RPGA 1 model that followed up the original RPG 1 and added a calendar function. A distinctly modern feature in this historically derived timepiece is the sapphire insert in the dive-scale bezel, a hallmark of contemporary Fifty Fathoms models, whose domed profile combines with the glassbox-type sapphire crystal to add depth to the watch’s face.

Caliber 1151 is on display behind the sapphire caseback.

Beating inside the 300-meter water-resistant case is the self-winding Blancpain Caliber 1151, a manufacture movement found in many Fifty Fathoms watches, including another 1960s tribute piece, 2017’s MIL-SPEC edition. Among its notable attributes are its lengthy four-day (100-hour) power reserve, stored in two series-coupled mainspring barrels, its NAC-coated rotor with a cartouche-shaped aperture and an engraved Blancpain logo; and its balance spring made of low-density, shock-resistant, magnetism-impervious silicon. The latter feature negates the need for the soft iron inner case that protected this watch’s historical predecessors from the ill effects of magnetic fields, and has allowed Blancpain to put the finely decorated movement on display behind a clear sapphire caseback.

Limited to 500 pieces, the Blancpain Tribute to Fifty Fathoms No-Rad is mounted on a “tropical” black rubber textured strap, a material chosen for diving durability. The watch is priced at $14,100.