The Radiomir is the first watch designed by Officine Panerai as a prototype in 1936 at the request of the Royal Italian Navy, which wanted to be supplied with “a special luminous watch for divers”. About ten of these prototypes were tested with excellent results, much better than those of other underwater watches then available. In 1938, following the acceleration of the military events, another more substantial order for watches was placed. The reliability of Officine Panerai, well proven on the wrists of the divers of the Italian Navy, was most of all due to the particular structure of the Radiomir case. The generous dimensions, with a diameter of 47 millimeters, and the cushion shape, with sides shaped to protect the dial, made it very resistant, while the three-part construction with a screw-on back and screw-down winding crown ensured maximum water-resistance. Other features of the Radiomir were the wire loop strap attachments, welded directly to the case, and its wide strap, water-resistant and long enough to be worn over the diving suits used by the frogman commandos. As for its name, this refers to the material used on the dial, a very luminous material – patented by Panerai – which made the Radiomir ideal for the underwater use for which it was designed.