CASE: Three-body, polished, unidirectional rotating Perspex bezel with dive timing indicator, protected screw-down crowns, screw down back, sapphire crystal.DIAL: Black with luminous steel Arabic numerals and baton indexes, outer minutes/seconds division. Luminous steel Alpha handsMOVEMENT: Cal.1315, rhodium-plated, perlage decoration, 35 jewels, straight-line lever escapement, monometallic balance adjusted to 5 positions, shock absorber, self compensating flat balance spring, Dial, case and movement signed, in excellent condition. NOS (New Old Stock)DIAM: 45 mm THICKNESS: 14 mmNOTE: Blancpain’s pioneering effort was named the “Fifty Fathoms” after the British measurement of 50 fathoms, or approximately 91.45 metres, which was at the time considered the maximum depth which a diver could achieve with the oxygen mixture then in use.