Important Swiss rose gold open faced deck watch Circa 1820

Rose gold duplex with calendar and equation of time by Frères Rey & Cie 
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An important, early Swiss 18 carat rose gold open faced quarter repeating jumping centre seconds deck watch with calendar and equation of time, Minutes du Soleil, circa 1820. Full plate movement, two hammers, two gongs, chain/fusee, open barrel for striking, double wheel duplex escapement, temperature compensated hairspring, extremely slowly swinging large three-armed balance, balance stop device. White enamel dial with Arabic numerals, rose gold minute and hour hands, rose gold sun hand for the equation of time indication. Plain case, bow punched 18K. Dial signed, dust cap signed. Comes with the, probably, original gold key and original three-piece wooden deck watch box.
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Diameter: 65 mm
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Weight: 258 g
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Signed: Frères Rey & Cie à Genève
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The movement, dial and case of this impressive pocket watch with the rare equation of time complication are in excellent condition. The case has no dents at all and therefore possibly a later production for the movement. Exceptional is the equation of time display with a rotating disc in the centre. The likewise unusual calendar with month and date is displayed through an aperture at 12 o’clock. This watch is one of the highest quality known deck watches from this time! Only one comparable watch is known, the Berthoud of the collection of the British Museum.
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The rare complication of the equation of time: “With the complication of the equation of time the wheel-driven aperture becomes a sundial. The aperture shows noon exactly every 24 hours. The sundial indicates noon when the sun is at its highest point. However, due to the inclination of the Earth’s axis and the eccentricity of the Earth’s orbit, the sun is not always at its highest point at the same time. A timepiece with an equation of time shows how large the difference is at any given moment”.