Omega Seamaster Planet Ocean 600M Co-Axial Master Chronometer Watch - 39.5 mm Black Ceramic Case - Unidirectional Bezel - Black Ceramic Dial - Black Leather Strap - 215.98.40.20.01.00139. 5 mm black ceramic case with helium escape valve, transparent back, unidirectional rotating bezel that includes a black ceramic triangle at 12 oclock, domed scratch resistant sapphire crystal anti reflective treatment on both sides, black ceramic dial with 18K white gold numerals, indexes and hands, as well as a date window at 3 oclock, Caliber Omega 8800 self winding movement with co axial escapement, chronometer, date, approximately 55 hours of