Rolex Oyster Perpetual, Submariner "660 ft=200 m", Ref. 5513. Produced in 1972 for NATO. Fine and rare, center-seconds, self-winding, water-resistant, stainless steel, NATO issue, military wristwatch with black bezel and a stainless steel Rolex buckle. Three-body, polished and brushed, screwed-down and engraved case back and crown, graduated revolving black bezel for the decompression times, "Triplock" winding-crown protected by the "Crown Guard". Engraved on the case back, thecodes: 0552/923-7697 429/72, in the middle, the Broad Arrow, which was used by the Royal British Air Forces. Black with tritium-coated round, triangular and bâton indexes. Tritium-coated "Lozenge" hands. Cal. 1520, rhodium-plated, 26 jewels, straight line lever escapement, monometallic balance, shock-absorber, self-compensating flat balance spring.Dial, case and movement signed.Diam. 40 mm. Height 14 mm. Notes Ref. 5513 Production of this reference started in 1962. The "T" on the dial indicates that the numerals and indexes are coated with tritium, to allow a nocturnal vision of the time indications. ote the "Lozenge" hands instead of the traditional "Mercedes" hands and bears rigid bars between the lugs. Together with Ref. 5517, these watches were made especially for the orth Atlantic Treaty Organisation, or ATO..