Reference 6239 was the very first Cosmograph Daytona introduced by Rolex, launched in 1963 and in production until around 1972. It was the brand’s first chronograph with the tachymeter scale engraved on the bezel. The watch offered in this catalogue represents one of the most rare versions, with the Daytona writing featuring a light blue color: a defect in the pigment has turned the signature, which was originally printed in white, to an attractive light blue shade, a phenomenon that may occur only in specimens in the 2-million serial range.