French smallest known 18K gold knife edge watch Circa 1905

Gold extremely flat Cartier rarity
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A rarity is this, probably smallest known, knife edge watch made by Cartier in Paris, France, circa 1905. The open faced numbered case of this watch was crafted from 18 carat gold, is extremely flat and has central white enamelled decoration on the back. The original engine turned dial has an inner ring with black Arabic hour numerals, outer minute divisions and blued steel Breguet hands. The very flat precision movement (2 mm) has a lever escapement.
Dial signed.
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Diameter: 32 mm
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Weight: 18.5 g
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Signed: Cartier Paris 
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Normally these watches have a diameter of 45 to 50 mm. This watch is the only listed piece in the woman’s size of 32 mm.