The production of the Panerai Firm for the Italian Navy was not only limited to watches. Since the beginning of the 20th century, Panerai were specialized in submarine precision instruments as compasses, bathometers, and diverses control instruments. In 1935, following the request of the Submariner Group of the Italian Navy, the permanent Commission studied the project of a special model of luminescent diver's wristwatch. The Commission provided a few models already available on the Market, but none of them were satisfactory as to their luminescence, water resistance and pressure. In March 1936, the Commission delivered a Radiomir wristwatch, which, after being tested in the sea at night and by day, turned out to be perfect. Ten examples of this model were immediately ordered and used during important manoeuvres where they obtained excellent results. According to the Navy, the date of 1936 was the year of the above events, but to date, experts and collectors believe that the first watches of this type appeared in 1938. Some illustrations of designs made by Panerai, are dated 30 October 1938 and show a waterproof case containing an ordinary watch. That same year, according to a famous collector of military watches, another prototype was produced, but for presentation only; it beared a dodecagonal bezel with the inscription "Officine Panerai Brevettato" and a transparent back showing the movement. Was it made in 1936 as the Navy says or in 1938 as asserted by numerous experts and the Officine Panerai ? Both are probably right, and, considering the political-military situation at that time, it may very well be that Panerai, after having created the first prototype, suspended their research, destroyed or left aside the designs, before taking up again the project two years later by launching the actual production, since the Navy required more watches. It could be that Panerai made a prototype in 1936, but the real production was launched two years later with some modifications. We may then consider that the first model was produced in 1938. It was the large waterproof model we know today, but featured an anonymous black dial with luminescent Roman and Arabic numerals as well as indexes. The movement was a Cortebert "ebauche", signed Rolex, mechanical with manual winding, the glass was in perspex, similar to that of compasses and bathometers. The bracelet was a large leather belt which was greased before being fixed on the watch. The graphic disposition of the dial may indicate that a small series of military wristwatches was produced by the Geneva Firm rather than by Panerai. However, in a letter written by Rolex, dated 11 January 1990, to the formerly mentioned italian collector Francesco Ferretti, it is said: "We have to clarify that Rolex never produced any military watches. The only exception would be the Radiomir Panerai, made by our agent in Florence, for the Italian Navy. Rolex provided only the movements and the screwed winding-crowns, which explains why these watches do not bea r the name of our brand". The major difference between the first series and the following ones, is essentially the dial: instead of the luminescent Roman and Arabic numerals of the former model, the new one bea r s four large Arabic numerals placed at the four cardinal points and large indexes made with diverse superposed plates fitted together : the bottom plate is luminous with "Radiomir" or "Luminor". The dial plate is pierced, so that the numbers are visible through the slots. Later, Panerai noticed that Radiomir was slightly radioactive, so they changed for Luminor, a new composition containing tritium. This innovation allowed Panerai to resolve the problem identified by the commandos during tests: a rather severe difficulty in reading the dial in extreme conditions. The two above described models were the first to be used by divers in war missions: one with Arabic and Roman numeral display, the other with Arabic numerals at the cardinal points. From 1939 onwards, the latter definitively replaced the first. The inscription "Radiomir Panerai" does not appear systematically. As a matter of fact, during certain war missions, it was more secure to wear an anonymous watch. The second evolution of Radiomir Panerai was in the lugs. The weakness of wire lugs caused many problems to users. Panerai redesigned the case by adding over-sized parts. The third evolution occured in the 1940's: the watertightness of watches was not always satisfactory because of the winding-crown mechanism. Panerai developed an ingenious lever device which kept the winding-crown pressed against the case, allowing watertightness to 200 meters, which, for evident military secrecy, would only be patented in Bern in 1956, after the end of the War. Panerai developped many other models, in limited editions of 30 pieces, for the Navy of different other countries. Among the new series of Panerai watches, the first models were made in a li mited edition of' 300 examples in 1992. In 1993, to please numerous worldwide collectors, the famous Luminor and the Mare Nostrum were re-edited in limited editions. In 1997, Officine Panerai was bought by the Vendome Group, and continued to reproduce models launched at the beginning of the 1990's, as well as the prestigious Luminor Marina, the GMT, the Submersible, the Power Reserve, the Historique and the special limited edition Sylvester Stallone Sly Tech.