French/Swiss 18K gold knife edged lever watch Circa 1912

Yellow gold open faced dress watch
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A thin French 18 carat yellow gold open faced knife edged (montre couteau) keyless pocket watch made by Cartier in Paris, circa  1910-1915. The rhodium plated movement made by the European Watch & Clock Co. Inc. in Switzerland with a lever escapement and eight adjustments. Silver dial with bold Roman hour numerals, an outer minute track and original Breguet hands. The case with a black enamelled, snap on back and the monogram P.R. Dial and movement signed.
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Diameter: 47 mm
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Signed: Cartier Swiss
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Couteau is the term used by Cartier in their manufacturing records to describe the type of ultra thin watches with knife edged cases, open faced or hunting cased models. These watches, with thicknesses of less than 4 mm for the open faced and less than 5 mm for the hunting cased version, are among the thinnest mechanical watches ever produced.
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For these thin watches from the first half of the 20th century, Cartier used movements from Edmund Jaeger (Jaeger-LeCoultre), who had just invented a movement only 2 mm thick. In the 1920s, Cartier and Jaeger formed a joint venture, the European Watch & Clock Co., whose signature can be found on many Cartier movements. Movements were further sourced from Vacheron & Constantin, who, from 1940, utilized a movement which was only 1.31 mm thick.