French Art Deco jumping hour chronoscope watch Circa 1930

Gold dress watch by Vacheron Constantin
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A very fine French two-colour gold jump hour keyless lever chronoscope watch, circa 1930. This timepiece features a cal. RA 17 PC damascened movement with lever escapement, 18 jewels, bimetallic compensation balance, and is signed and numbered Vacheron & Constantin Genève, with patent number 130191. The dial is silvered with an engine-turned design, a lower silvered banner signed Vacheron & Constantin at the centre, a tapered aperture for jumping hours, and outer long apertures around the circumference with a triangular-shaped ruby indicating minutes, all enclosed by a flat white gold bezel. The case is made of 18k white and yellow gold, with a white gold calibrated bezel featuring a yellow gold chamfered outer edge, a white gold case band, a white gold snap-on back with a yellow gold chamfered bezel, a yellow gold pendant and a shaped white gold bow, and is signed and numbered Vacheron & Constantin Genève.
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Diameter: 44 mm
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Signed: Vacheron & Constantin Genève
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This example is truly exceptional, boasting a two-tone case in beautiful condition and a unique triangular-tipped revolving ruby minute indicator.
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The watch dial is in good condition, although there is some tarnishing to the silvering of the outer aperture. The case is in lovely condition, retaining good definition to its angles and edges, with only light scuffs. However, the crystal is slightly loose. The movement is running and appears to be in good condition, but it would probably benefit from a service.
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Accompanied by an Extract from the Vacheron Constantin Archives confirming the date of manufacture in 1930. In 1925 the watchmaker Robert Cart created a unique complication which he called, the ‘Jumping Hour’ or ‘chronoscope,’ under patent number 130191. This was a brilliant system of jumping hours and wandering minute indication.
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Breguet and Vacheron & Constantin were particularly enthusiastic about adopting the mechanism, which came in two types. Breguet favoured the first type with the wandering hours, while Vacheron preferred the second type with the fixed indication aperture at 12, as evident in the present watch.
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A chronoscope is a type of watch with a stopwatch function. It’s a more subtle version of a chronograph, with two subdials instead of three. The chronoscope is an elegant and practical choice for watch enthusiasts who appreciate the functionality of a stopwatch but prefer the aesthetics of a classic watch.