ROLEX, "Oyster Cosmograph", "SIGMA DIAL", case No. 5523146, Ref. 6265/6263, water-resistant, stainless steel wristwatch with steel bezel, round button chronograph, registers, tachometer and a stainless steel Rolex Oyster folded bracelet Ref. 78350/19. Made in 1978. Accompanied by the original box. CASE : Three-body, polished and brushed, screwed-down case back, buttons and Triplock winding crown, tachometer graduation on the bezel to 200 units per hour. DIAL : Bicolor black and silver with applied baton indexes and luminous dots, outer minutes/seconds divisions, subsidiary guilloché dials for the seconds, the 12-hour and 30-minute registers. Luminous steel baton hands. Movement: Cal. 727, rhodium-plated, 17 jewels, straight-line lever escapement, monometallic balance with Microstella regulating screws, adjusted to 3 positions, shock absorber, self-compensating Breguet balance spring. Dial, case and movement signed, in good condition DIAM: 37 mm. THICKNESS: 13 mm. NOTE: A Sigma dial is a Rolex dial named for the letters printed at the bottom of the dial at 6 o’clock. Most Daytona dials are marked with “T Swiss T,” however a Sigma dial is marked “σ T SWISS T σ.” These Daytona’s get the name from the two O shaped symbols on each side of the “T SWISS T.” Dials marked with this lettering are fitted with solid gold markers, unlike other dials which may use steel or other materials. Sigma dials come in both yellow and white gold and are very rare. StartPrice : 20000