Swiss very rare prototype observatory chronometer Circa 1930

Prototype deck chronometer
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An observatory chronometer deck watch, probably a prototype and one of five pieces made by Movado in Switzerland, circa 1930. The dial has Arabic hour numerals, an outer minute track, a subsidiary seconds dial at 6 o’clock, a power reserve dial at 12 and blued steel moon hands. The movement has a chronometer escapement, a large gold screw Guillaume balance, blued flat hairspring with a Phillips terminal curve and a faceted diamond end stone.
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Diameter: 65 mm
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Signed: No name
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The present timepiece is one of only a few observatory chronometers produced with this caliber and one of five that were prototyped with a spring detent escapement. All other tested chronometers had an anker escapement. The movement is in its original condition and has never been cased and sold. Some of these watches were also submitted to the chronometer trials at the National Physical Laboratory in Teddington. Developed in 1927, the caliber was specially designed for observatory competitions. In addition to the enormous size of this movement, ∅ 65 mm, the most striking thing about this construction is that the exquisitely finished escapement section is designed separately as a removable assembly. The advantages of this concept are the improved handling of the precision regulator, as well as the interchangeability of the components.