The company went on to make luminous devices for firing naval guns at night, timing gauges and mechanical calculators. An area which differentiated Panerai watches was the peerless luminescence of its dials. This visibility in restricted light was courtesy of a luminescent paint composed of zinc sulphide, mesothorium and radium bromide, named Radiomir and patented by Guido Panerai in 1915.
In 1935, Officine Panerai supplied the Royal Italian Navy with precision pocket stopwatches for military use. One year later, in 1936, the company produced a prototype diver’s watch. This was put into serial production in 1938 and the Panerai Radiomir said to be the first military diver’s watch in history, was born.
The 1938 Panerai Radiomir measured 47mm in diameter, had a luminous dial, screw-down winding crown and distinctive wire loop strap attachments. These elements can be seen on many of the present-day models. However, the 1938 models contained a Rolex movement and remain very collectable, attracting high auction prices. Indeed, for the Panerai aficionado, a three-part diver’s set consisting of a watch, wrist mounted compass and wrist-mounted bathometer (depth gauge) are very desirable and much sought after.