Swiss observation chronometer in mahogany box Circa 1940

Chronometer for the British Ministry of Defense
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A British Ministry of Defense observation chronometer, with reference HS527-3637, made by Rolex in Genève, Switzerland, circa 1940. The watch is housed in a well preserved mahogany box, bearing the British military hallmark. The open faced case is made of metal and is engraved with the B12890 hallmark. The silver plated dial features an outer ring with Arabic numerals for the hours, a subsidiary dial at six o’clock with Arabic numerals for the seconds, and Breguet steel hands. The movement boasts a lever escapement calibre 548, produced by Rolex.
The watch’s dial and movement are both signed, attesting to Rolex’s commitment to excellence and precision.
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Diameter: 52 mm
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Signed: Rolex, Swiss Made
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Rolex is a luxury watch brand that was founded in 1905 by Hans Wilsdorf and Alfred Davis in London, England. Originally called Wilsdorf & Davis, the company later changed its name to Rolex in 1908.

Rolex has a rich history of innovation and achievement in the watchmaking industry. In 1910, Rolex was the first watch company to receive the Swiss Certificate of Chronometric Precision, which is awarded to timepieces that pass a series of rigorous tests for accuracy and reliability.

In 1926, Rolex introduced the Oyster, the world’s first waterproof wristwatch. This was followed by the introduction of the Perpetual rotor, which automatically winds the watch’s mainspring as the wearer moves their wrist.

Over the years, Rolex has continued to innovate and push the boundaries of watchmaking technology. Today, Rolex is one of the most recognized and respected luxury watch brands in the world, known for its precision, durability, and timeless style.
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The British Ministry of Defense observation chronometers were essential tools for military operations during World War II. These watches were used to synchronize the movements of troops and equipment, as well as to coordinate air raids and naval operations. The accuracy of these timepieces was crucial to the success of military operations, and Rolex was one of the few watchmakers capable of producing such precise instruments.