Swiss 18K gold quarter repeating musical pocket watch Circa 1820

Gold open faced duplex pocket watch 
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A very fine, Swiss 18K gold quarter repeating musical pocket watch, circa 1820.
The music plays on the hour or at will and double-wheel duplex escapement. An Empire, engine-turned and polished case, ribbed band, bolt at 1 o’clock to lock the repeat and at 7 to activate the music. Hinged gilt brass cuvette with apertures for winding and hand-setting. White enamel dial, Breguet numerals, outer minute track. Blued steel Breguet hands.
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A gilt brass movement, two-train, with a standing barrel for the going train, double-wheel duplex escapement, plain gold three-arm balance, flat balance spring, index regulator, repeating on gongs activated by depressing the pendant. Sur plateau musical movement, 19 tuned, vibrating blades acting on both sides of the pinned disc, music/silence lever at the edge of the cuvette beneath the back cover. Dial plate punched P&M, cuvette signed Janvier a Paris, case and movement number.
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Diameter: 57 mm
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Signed: Piguet & Meylan  Geneva
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Slightly restored soft enamel on the dial.
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This watch by Piguet & Meylan has the unusual and rarely used double-wheel duplex escapement. The double-wheel duplex originated in France and is particularly suited to thick watches, it was found to be favour more in England than in France for this reason. Breguet used this escapement in a small number of his watches. A scratched inscription in French on the dial plate beneath the musical teeth states: The escapement of this watch was made by J.B. master horologer in 1826. As this watch evidently passed through Janvier’s workshop, it is therefore possible that the escapement was upgraded there from the usual cylinder escapement found in this type of watch.