Very rare Swiss 18 carat gold digital pocket watch Circa 1977

Gold lever watch with linear perpetual calendar 
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An extremely fine and very rare Swiss 18 carat yellow gold open faced keyless lever dress watch with linear perpetual calendar and moon phases, circa 1977. Accompanied by the original presentation box, the Certificate of Origin, a hang tag, Patek Philippe (Japanese) service guarantee card, a pouch and booklet. The polished and brushed, modern case with a concave bezel, correctors on the flat band and an inverted U shaped bow.
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Brushed silver dial with applied yellow gold baton indexes and Arabic 12, outer minute divisions, an aperture for the digital display of days of the week, months and the date at 12 o’clock, subsidiary seconds with concentric moon phases at 6 and yellow gold dauphine hands. A rhodium plated movement with Geneva striping decoration, stamped twice with the seal of the Geneva quality mark, 18 jewels, a straight line lever escapement, monometallic balance adjusted to heat, cold, isochronisms and five positions, self compensating blued steel Breguet balance spring and swan neck micrometric regulator. Dial, case and movement signed.
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Diameter: 46 mm
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Signed: Patek Philippe Genève
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The linear digital calendar is a calendar in which the date is displayed in a single aperture, allowing for a clear dial to be read at a glance. This type of display became popular in the Art Deco period and is most often found in watches destined for the Anglo-American market. This kind of calendar then became known as the American perpetual calendar.