At 17mm the 512 is not really a thin watch but it is 42mm. The more traditional styled Radiomir 338 is thinner at 15mm.
"IN ABOUT 1940, THE PANERAI WORKSHOPS IN FLORENCE PERFECTED A NEW CASE, designed to meet the increasing demands of the commandos of the Italian Navy. The case was a development of the one presented in 1936 which is known today as the Radiomir – a term which originally referred to the luminous material patented by Panerai to make the dial readable in the dark – but it presented some innovations designed to make its construction even more solid and hardwearing.
In the new case the strap attachments were no longer formed from a strong piece of steel wire bent and welded to the caseband, as they had been previously. This design might expose the watch to the risk of the strap coming off in the course of the extreme operations which commandos were called upon to undertake when on board their underwater assault craft. In the 1940s version, on the other hand, the lugs were larger and much more solid, being milled from the same block of steel as the case, of which they were an integral part. As well as the strap attachments, the system of attaching the strap was also changed, becoming much simpler and more secure. While previously it had been necessary to sew the leather round the wire strap attachments, the new construction had little holes in the lugs themselves in which a small tubular bar could be fitted, having been inserted through the loop of the
strap. This was a more modern solution, which also meant that the leather strap could be replaced easily. As well as the modification to the strap attachments, other changes altered the Radiomir case in a definitive way, presaging the subsequent development of the shape of the Luminor case which came out a few years later. The cushion-shaped outlines were now less accentuated. The winding crown was slightly larger and cylindrical rather than troncoidal. The overall thickness of the watch increased from about 15 mm to almost 17 mm.
So was born the Radiomir 1940 case which Officine Panerai is presenting again today – with the same design but in a thinner version – in new models of the collection, watches endowed with the strength and fascination that only being a part of history can convey. The Radiomir 1940 in steel has a case 42 mm in diameter with the P.999 hand-wound movement, the smallest and thinnest in the wide range of calibres produced by the Officine Panerai manufacture in Neuchâtel. The P.999 movement, visible through the sapphire crystal window set in the back, has a power reserve of 60 hours and a balance which oscillates at 21,600 vibrations/hour (equivalent to 3 Hz). The Radiomir 1940 is supplied with a black alligator strap, and it is part of the Historic Collection."
