Exceptionally rare American keyless pocket watch Circa 1950

With patent Montgomery dial and special escapement by Hamilton
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A fine and exceptionally rare American 10 Carat gold filled keyless pocket watch with patent Montgomery dial and special escapement, circa 1950. Rhodium plated movement, Geneva Striping decoration, now fitted with a Clifford magnetic escapement with à Mumetal pierced escape wheel and spring blade detent type resonator. White enamel Montgomery dial with large Arabic numerals, outer minute divisions and individual Arabic minute numerals, subsidiary seconds, original blued steel spade hands. Case with screwed down back and bezel with reeded and dot decoration, large bow. Dial, case and movement signed. Comes with original Hamilton box and guarantee.
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Diameter: 51 mm
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Signed: Hamilton Railway Special
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Due to its experimental nature and delicacy, the timekeeping of this watch can be intermittent, with a duration of approximately 10 hours. This fascinating watch is one of only two known Hamilton watches that were sent by The Hamilton Watch Company to Horstmann Clifford Magnetics Ltd in Bath, England, for modification. 
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The Clifford Magnetic Escapement invented by Cecil F. Clifford, BSC, FBHI, in 1938, it was experimented upon during World War II with the aim of producing a silent time bomb for naval use. The theory was that as the escapement does not ‘tick’ it would be undetected by sonar. The escapement consists of a flat pierced sinusoidal escape wheel made of a magnetisable material called ‘Mumetal’, mounted horizontally, and a flat upright ‘detent’ terminating in two prongs allowing the escape wheel teeth to pass through. After the war, Clifford approached various firms with the idea of using the silent escapement in clocks and watches. He eventually joined the company of Horstmann Gear Ltd, a maker of mechanical clocks. In 1948 the company became Horstmann Clifford Magnetics Ltd, producing clocks and watches with magnetic escapements. The company never actually went into production with magnetic escapements but instead approached various companies to take out production licenses.
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The Hamilton Watch Company was approached and sent two watches over to England for the escapement to be fitted, the present watch is one of these pieces. Although it was reported that the watches performed well, Hamilton did not take out a manufacturing license and in fact neither did any other company. HCM achieved great success after 1952 with electronic clocks and watches with ‘tuning fork’ mechanisms and in fact all tuning fork clocks made in the 1960s had magnetic escapements similar to the Hamilton prototype that were linked to an electronically operated transistorized mechanism. With the advent of quartz technology, the escapement became obsolete by 1970.
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Montgomery dial designed by H.S. Montgomery and patented on April 20, 1920. This dial is distinctive in that every minute marker has an Arabic numeral written in full.