The transition from the Rolex Chronograph ref. 6238 to the Cosmograph ref. 6239 represents one of the most significant developments in the history of the Daytona. Introduced in the early 1960s, the ref. 6238 was the final expression of Rolex's traditional chronograph design, with its tachymeter scale printed directly onto the dial and subsidiary registers generally finished in the same colour as the dial itself. Its successor, the ref. 6239, introduced contrasting chronograph registers and, crucially, relocated the tachymeter scale to an engraved steel bezel. Although the underlying case architecture remained remarkably similar, these changes transformed the appearance of the watch and established the visual identity of the Cosmograph Daytona. Both references were offered simultaneously for several years, and their shared construction meant that certain components could be interchanged.

Dating to 1963, this unusual example combines a ref. 6238 case and movement with an early ref. 6239 Cosmograph dial and engraved tachymeter bezel. The dial is particularly noteworthy, belonging to the rare early variation described in Pucci Papaleo's Ultimate Daytona as the 'Nero' dial with floating logo. Its defining characteristics include the unusually low positioning of the dial inscriptions beneath the coronet, with the ROLEX signature printed in white and the COSMOGRAPH and DAYTONA inscriptions executed in silver. The dial also features the early – T SWISS T – designation at six o'clock, a characteristic associated with approximately 1963 production and therefore consistent with the date of the underlying ref. 6238. While its precise history cannot be established, the most plausible explanation in our minds is that the dial and bezel were exchanged by a retailer during the early years of the Daytona's production. With the newer Cosmograph proving more commercially appealing than the traditional ref. 6238, such a conversion would have allowed a dealer to offer an older watch with the appearance of Rolex's latest chronograph. The result is a fascinating period configuration that captures the moment when the traditional Rolex chronograph gave way to the Daytona.