Elegant Swiss Staybrite stainless steel lever watch Circa 1950

Stainless steel keyless pocket watch 
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A fine, rare and elegant Swiss Staybrite stainless steel open faced keyless pocket watch made by Vacheron Constantin SA in Geneva, circa 1950. The jewelled movement with a lever escapement. Two tone silvered sector dial with applied baton and Arabic hour indexes, an outer minute track, engine turned subsidiary seconds at 6 o’clock and gold hands. The plain case with a snap on back. Dial signed, case and movement signed and numbered.
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Diameter: 46.5 mm
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Signed: Vacheron & Constantin Genève Swiss
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Reference 51400.
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Staybrite is the name of a steel alloy containing 0.2% carbon, 18% chromium and 8% nickel. It is a stainless material that takes a fine polish and is therefore often used for making watch cases. It is probably the type of stainless steel that has been most widely used by watch companies, from the 1930s onwards.