French firegilt pre-balance rock crystal watch Circa 1660

Extremely rare open faced watch
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A very fine and extremely rare pre balance rock crystal watch, circa 1660.
Firegilt brass frame case, facetted rock crystal cover and back, lobed cover with copper dial, firegilt, florally engraved centre, engraved Roman hours, finely cut blued iron hand, full plate brass movement, frosted, gilt, baluster shaped movement pillars, chain fusee, verge escapement, plain two arm steel balance without spring, florally pierced and engraved balance cock, top lock with blued click work.
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Diameter: 45 mm
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Weight: 81 g
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Signed: Duhamel a Paris