The present watch is from the very first series of the celebrated reference 6239 showing distinctive features found only on the earliest examples:
-the dial without the designation "Daytona" as found on later series
-the double Swiss designation, e.g. "Swiss" printed visibly between the 12 hour register dial and the 6 o'clock index, a second "Swiss" below the 60 seconds scale to the edge of the dial, hardly visible while the dial is mounted onto the watch
-the subsidiary dials with sunk engine-turned centres surrounded by a blank raised outer ring for the indexes
-the blank metal bezel calibrated for one unit up to 120, intervals of 2 units from 120 to 150 and intermediate calibration 225, 250 and 275
-the case back with reference number 6238, a common feature for the earliest Cosmographs
Made in 1963, the year of introduction of the model, the rarity of this so-called "Double Swiss" Cosmograph wristwatch is furthermore enhanced by its very well preserved, original condition.
Reference 6239, the very first model of the celebrated "Daytona" series, succeeded reference 6238 and could be found in sales catalogues in Europe as of 1964. It is thought though that the model was available in the US already in 1963. Available in stainless steel, 14K and 18K gold, reference 6239 was the firm's first chronograph with the tachometre scale engraved on the bezel and the subsidiary dials printed in a different color than the main dial for better readability. The dials of the early models featured only the designation "Cosmograph", referring to the outer space travels of the early 60s. The "Daytona" was added on later series to mark Rolex's sponsorship of the renowned NASCAR stock car race.
For detailed descriptions and illustrations of the dial and bezel variations of reference 6239 see Rolex Daytona - a legend is born by Carlo Pergola, Stefano Mazzariol, Giovanni Dosso, pp. 44 - 61. Different versions of reference 6239 in regard to case material and dial layout are furthermore described and illustrated in I Cronografi Rolex - La Leggenda, Pucci Papaleo Editore, pp. 296-303.