The present watch is a rare example of reference 3668, featuring a highly unusual, beautifully aged silvered dial omitting all technical outer scales (tachymetre, telemetre or pulsometre) that one would usually expect on such a watch. Consequently the entire layout could be modified by moving the numerals further to the edge and enlarging the subsidiary dials. This results in better readability, both of the fifths seconds on the outer scale and the indications on the subsidiary dials. Interestingly due to the different dial proportions, the watch appears to be larger.
After years of success with the newly invented Oyster model, a wristwatch with screw back and screw down crown, Rolex launched the first Oyster chronograph, reference 3481, in 1939. Immediately afterwards, its larger successor, reference 3668, was presented and remained in production for very few years only.
Produced in small quantities, reference 3668 takes a unique position in the history of Rolex chronographs as it clearly stands out with its exclusive design incorporating a reeded bezel chased with hour markers.
Another example of reference 3668 with a virtually identical dial is illustrated and described in The Best of Time - Rolex Wristwatches by James M. Dowling & Jeffrey P. Hess, p. 220.
Different versions of reference 3668 are illustrated in I Cronografi Rolex - La Leggenda, Pucci Papaleo Editore, pp. 194 - 198.