Rolex first attempt to release an Oyster Cosmograph with screw down chronograph pushers happened in 1965 with the released of the 6240 , according to Osvaldo Patrizzi, the 6240 was a prototype model, however it lasted 4 years in the Rolex brochure and was replaced by the 6263. The major difference between these two watches was that the 6240 were released with the Rolex caliber 722 while the 6263 were fitted with the newer Rolex caliber 727. Also, the 6240 has a thinner minute hand
In 1965, the first nail button model production, and continued until 1969 production of 722 movement.
This watch is a Rolex mysterious objects in a limited period of time, only a few appear in the directory of the time.
Some theories have been proposed to introduce these screw button:
Seems to be the most conclusive prevent accidental start time function in high-risk situations (diving, there is dust or other aggressive material). The first time, the inscription on the emergence of a dial-up of the 6240 oysters, previously described only in 6238 and pump timer button.
Eligible oysters, ensuring the improvement of water resistance is due to the existence of spiral button and a 7 mm winding up from the 700 Series crown, rather than install a 600 series pump is equipped with six millimeters examples button.
This model can be with the main black Bakelite panel, but it is likely to have the first example Rolex (1965-1967) and the metal panel 6239, as the first standard model Bakelite panel 6241 that remain in production 67 to 70 years are the same in various ways to the 6239, apart from the panel.
Movement contrary to the three models in the second half of the 60 (including 6239) are still on the 722 from Article 72B from its retained the same number of changes per hour – 18000.
Back to 6240, should be borne in mind the example of steel dark dial-up, the earliest, with silver counters, as well as those light-colored with a brown dial counters.