The present "Divomet" is one of the exceptional rare "Manomètre Bourdon" devices for which Rolex obtained Swiss Patent No. 324229 on 15 September 1957, UK Patent No. 771'204 was published on 27 March 1957 (photocopies of Patents No. 324229 and 771'204 and the correspondent technical drawing will be delivered with the "Divomet").
This pressure gauge was designed for measuring the depth of oceans or lakes, one hand indicating the feet 10 by 10, the second hand showing the relevant feet. A bracelet passes through the circular crankcase which contains the mechanism as found in a Bourdon manometer.
Unknown to literature, the Rolex "Divomet", certainly standing for "diving meter", never went beyond the prototype stage. Preserved in like new overall condition and fitted with a bright-coloured bakelite insert, normally associated with Rolex GMT-Master wristwatch ref. 6542 launched in 1954, the present "Divomet" was most likely one of these prototypes and has never actually been used.
Based on the year when Rolex invention of a Manometer Bourdon was submitted, 1955, it can safely be assumed that this ingenious device was originally developed for Auguste and Jacques Piccard's deep sea diving expeditions. Most notably is certainly the "Deep Sea Special" which was successfully put on trial in 1960 when Jacques Piccard and Navy Lieutenant Donald Walsh descended in the "Trieste" to the deepest known point on Earth - the Challenger Deep in the Mariana Trench in the Pacific Ocean. The two men made the deepest dive in history: 10,915 meters (35,810 ft) with a "Deep Sea Special" fixed to the outside of the bathyscaph. The watch hold up to a pressure of 1,150 atm or 1,150 kgs per cm2.
The Bourdon pressure gauge uses the principle that a flattened tube tends to change to a more circular cross-section when pressurized. Although this change in cross-section may be hardly noticeable, and thus involving moderate stresses within the elastic range of easily workable materials, the strain of the material of the tube is magnified by forming the tube into a C shape or even a helix, such that the entire tube tends to straighten out or uncoil, elastically, as it is pressurized. Eugene Bourdon patented his gauge in France in 1849, and it was widely adopted because of its superior sensitivity, linearity, and accuracy.
(Sold without strap).