Swiss 18K gold minute repeating astronomical lever Circa 1987

Gold dress watch with linear calendar and moon phases 
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A very fine and very rare Swiss 18 carat gold minute repeating astronomical keyless lever dress watch with digital American perpetual calendar and moon phases, circa 1987. Sold on January 31st, 1990. The rhodium plated movement with Geneva Striping decoration, 29 jewels, a counterpoised straight line lever escapement, monometallic balance adjusted to heat, cold, isochronism and five positions, self compensating Breguet balance spring with swan neck micrometre regulator and repeating on gongs activated by a slide in the band. Matte silver dial with applied gold baton indexes, outer minute divisions, an aperture for the days of the week, the months of the year and the date, subsidiary seconds with a moon phase aperture and original gold dauphine hands. A polished and brushed case. Dial, case and movement signed, case and movement numbered. Accompanied by an Extract from the Archives, a push pin and leather pouch.
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Diameter: 51 mm
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Signed: Patek Philippe Genève Swiss
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The linear digital calendar or so-called American (perpetual) calendar is a calendar in which the date is displayed in a single linear aperture, allowing for a legible dial to be read at a glance. This type of display was invented in the early Art Deco period and is most often found in watches destined for the Anglo-American market. This kind of calendar became popular once again after the Second World War.