The most striking design feature of this model, Ref. 6538, is the large crown with no crown guard shoulders. Now known to collectors as the 'big crown James Bond', this model is especially rare, as Rolex would replace the large crown (with a diameter of 8mm.) with a smaller one (with a diameter of 6mm.) by the end of the 1950s. For this reason, the larger crown with the word 'Brevet' commands more attention and more value in today's collecting world.
The present example, a second-generation Ref. 6538, shows the phrase 'Officially Certified Chronometer' below the word 'Submariner'. It is interesting to note that the earlier generation Ref. 6538 featured the same movement, but was not designated as such on the dial. This expanded signature is commonly known as the 'four-line' dial and is highly collectible. The beautiful chocolate-tone dial on the present lot makes it even more rare and interesting to collectors.
The nickname 'James Bond' comes from the fact that Submariner models without crown guards were frequently used in the Bond movies. In fact, it is likely that the Submariner used in some of the early Bond films, including 'Dr. No', 'Goldfinger' and 'You Only Live Twice', were examples of this model, Ref. 6538. Today any Submariner without crown guards, regardless of the reference or year of production, is referred to as a 'James Bond'.
For more information on this model and on the Submariner family of watches, Skeet, M. & Urul, N. Vintage Rolex Sports Models, pp. 20-25. For a similar example, see p. 31 of the same text.