Rolex Oyster Cosmograph, Ref. 6263, 1980's, produced from 1961 to 1988, first model with screwed buttons in 1976. Fine, stainless steel gentleman's wristwatch, with round button chronograph, register and tachometer. polished, satined, screwed back and buttons, waterproof, tachometer graduation on the bezel. 278 bicolour beige and black, with indexes + auxiliary dials for the seconds, the 12 hours and 30 minutes registers. "Bâton" radiumed hands.