In the 1930s, the men in the Italian Royal Navy's Gamma Group, carried out their maneuvers astride human torpedoes a.k.a. "pigs" or indeed "black seals". The first modern Panerai Radiomir watch honoring ref. 3646 from the late 1930s was launched in 2004 with a 45mm —the original Radiomir watches had a case measuring 47mm in diameter— stainless steel cushion-shaped case with detachable wire lugs, display case back, black matte sandwich dial with superluminova, onion-shaped crown, gold calf strap with beige contrast stitching, large pin buckle and the OP XI hand-wound movement —based off of the ETA 6497/2 but with a swan neck regulator. This Panerai, was released under the 'Radiomir Black Seal' name and usually referred to by Paneristi as the PAM 183. Today, the PAM 183 includes the 'Black Seal' writing at 12 o'clock under the word 'Radiomir' instead of at 6 o'clock as it did when it was launched in 2004.