The reference 6238 is known among collectors as the "Pre-Daytona". It was the immediate predecessor of the 6239, the first Rolex Cosmograph Daytona. The 6238 first appeared in Rolex catalogues in 1964 and remained through 1967. The watch was produced in stainless steel, 14k and 18k gold with the 14k gold model destined for the North American market. The reference 6238 was outfitted with the 722 calibre which was an improvement over the earlier 72B.
This model is described and illustrated in I Cronografi Rolex- LA Leggenda, Pucci Papaelo Editore, p. 286.