Omega "Speedmaster Professional Mark IV", Automatic, No. 36261483, case No. 176.009. Producedcirca 1973.Fine self-winding, water-resistant, tonneau-shaped, stainless steel gentleman's wristwatch with date, round button chronograph, registers, tachometer, 24 hours with night/day indication, and stainless steel articulated Omega bracelet and clasp. two-body, polished and brushed, screwed-down case back with logo, hooded lugs. black with tritium-coated indexes, auxiliary dials for the seconds and the 12 hours registers, the 24 hours with night/day indication by means of an arrow on an under-disc, 60-minute register by means of a fourth cross-shaped central hand, outer tachometer graduation on a black ring under the crystal and outer 1/5th second scale, aperture for the date, mineral glass. "Bâton" tritium-coated white hands. Cal. 140, copper-colored, 22 jewels, straight line lever escapement, monometallic balance, shock-absorber, self-compensating flat balance-spring.Dial, case and movement signed. Dim. 42 x 45 mm. Approx. overall length 185 mm.