This is a rare Rolex 'Hermetique' or 'Submarine' as it became affectionately known, finished in silver and dating from the early 1920s. 
 
This early waterproof case design (patented by Rolex in 1922) pre-dated the Rolex 'Oyster' case still famous today that started in 1926, making this an unusual transitional model in Rolex’ history.
 
It was retailed by Cargills LTD of Ceylon (Sri Lanka). Cargills LTD were an import and wholesale business in Colombo Fort. The Cargills building is an architectural marvel. It was designed by Edward Skinner and constructed in 1906. A photograph is included in the images.
 
In January 1921 Jean Finger, a watch case maker of Longeau, Berne, Switzerland, was granted Swiss patent number CH 89276 for “a stem winding watch with a protective box”.
 
This design of waterproof watch had the virtue of simplicity, the watch was placed inside a larger case with a screw-down bezel which formed a hermetic seal. To wind the watch or set the hands the outer bezel was unscrewed, and the movement flipped out on a hinge allowing conventional crown usage. 
 
The case design had the major drawback that the bezel had to be unscrewed every day so that the watch could be wound. This was awkward for the user, whilst the case threads and the milling on the bezel wore quite quickly from this continuous use. Despite this, a number of manufacturers including Zenith and Eberhard produced watches using this case design. Hans Wilsdorf (Rolex president) must have liked the design of Jean Finger's hermetic case and bought some rights to the patent. 
 
He applied for a patent on exactly the same case design in Britain on 26 May 1922, which was granted British patent number GB 197208 “Improvements in and Relating to Watches”. Wilsdorf doesn't mention Jean Finger in his application, so the exact ownership of the patent is something of a mystery. An identical design had also patented by Frederic Gruen in the USA in 1918. A trademark “The Submarine” was registered by Hans Wilsdorf / The Rolex Watch Co. / Rolex S.A. / Tudor S.A. / Oyster Watch Co. on 31 March 1922.
 
A Rolex watch using this hermetic case design was produced from 1924. 
 
Both the outer and inner case are solid silver and the watch has a diameter of some 32mm. The coin edge bezel unscrews to reveal the hinged inner case. This pivots to allow the watch to be manually wound. The inside of the case back is signed Rolex, with Swiss hallmarking for silver and the reference number 3666. The inner case back opens to reveal the 'Rolex' Prima movement which has been recently serviced.
 
Full condition report below. Please see the images as these compliment and aid the description provided below.
 
Dial: 
The dial is enamel and is in decent condition. It has clear radium painted Arabic numerals. It is a sector dial with an inset central circle and sub-second dial. The railroad track around the exterior of the dial is clear and simple. It has a thicker line for each hour, whilst 9,12,3 and 6 have a diamond marker. The signing Cargills LTD Ceylon and Rolex is worn but visible. There are some hairline factures to the dial, but no chips or deep fractures.
 
Hands: 
The Radium syringe hands are original and are in excellent condition. They are thermally blued and are in excellent condition with no bending and very minimal variation in tone. The sub second hand is also original and thermally blued.
 
Glass: 
The crystal is a replacement which is in very good condition. 
 
Crown: 
The crown appears to be original and has wear to the plated finish. 
 
Case:
Main body of the case is solid, with wire lugs, with an inner case once the coin edge front is removed. The front section has a coin edge finish which is in aged condition. The thread is in good condition with it screwing down as it should. The lugs are in good condition and aren’t bent. 
 
Caseback:
The rear of the case is solid, with the inner case being exposed by un-screwing the front. 
The rear is in good condition with only light surface scratches and some tarnishing. The inside of the case back is in good condition. It has Swiss hallmarking for sterling silver and is signed with the Rolex name and reference 3666.
 
Inner case:
The inner case is hinged. The bar is worn and means you need to be careful and hold the inner case whilst you wind the watch.
 
Strap: 
The watch is on a new genuine leather black Meyhofer single piece strap. 
 
Movement: 
The movement is a great quality Rolex Aegler calibre for the era. It is a Rolex Prima movement, which was top of the range. It has a jewel count of 15 and is marked as adjusted to 6 positions and temperature. 
 
The movement has been recently serviced by us. It has a daily gain of +60 seconds, with an amplitude of 290 degrees and a beat error of 1.5m/s.
 
Case dimensions: 
Case width: 32mm
Case length: 32mm 
Case length lug to lug: 36mm
Case Depth: 9.5mm
Lug width: 12mm