English gold precision watch with six minute tourbillon Circa 1905

Extremely rare and import watch, it comes with a fordsham certificate
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An extremely rare and important, heavy precision pocket watch with six minute tourbillon, circa 1905. To the best of our knowledge only 4 watches exist that are fitted with a six minute tourbillon. This watch was submitted three times for chronometer testing at Kew Observatory and reached 82.9 points in the final test. The watch comes with a Frodsham certificate and copies of Kew Observatory archive extracts. 18k gold case, tiered, polished, case maker’s punch mark “HMF” (Harrison Mill Frodsham), turnable pendant. Enamel dial, off-white, radial Roman numerals, auxiliary seconds, signed, blued spade hands. 3/4 plate movement, ébauche: Nicole Nielsen, frosted, gilt, numbered, signed, screwed chatons, finely polished three arm steel tourbillon cage of Nielsen type 1 with polished screws, lever escapement with a counterpoised gold weight, Guillaume gold screw compensation balance.
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Diameter: 60 mm
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Weight: 169 g
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Signed: Charles Frodsham, London