Rolex chronographs have always been sought after. From circa 1937 Rolex has added some chronographs at the end of their sale catalogue and immediately the became a succes. From the beginning of the production of their iconic reference 3525 Oyster Monobloc, Rolex combined waterproofness together with chronometer quality movement. After WW2 Rolex continue to improve their chronographs and launched the Datocompax, a full calendar chronograph in a oyster case nicknamed after Jean Claude Killy alias "Killy". In the 1950 Rolex continued to produce special chronographs and early 1960 the legendary Rolex Daytona got introduced. Lean everything about the "Killy" by studying my RPReport by following this link...