Swiss minute repeating perpetual calendar watch Circa 1973 

White gold minute repeating perpetual calendar watch
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A fine and extremely rare Swiss white gold open faced minute repeating perpetual calendar watch with moon phases, circa 1973.
Manual winding rhodium-plated counterpoise lever escapement movement, 29 jewels, mono-metallic balance with peripheral timing screws and blued Breguetbalance spring with terminal curb, wolf’s tooth winding mechanism, swan neck micrometre regulation system, two polished hammers repeating on two gongs.
Silvered dial, applied gold baton numerals, aperture for month, date and day in English,subsidiary dial indicating constant seconds combined with moon-phases, gold dauphine hands, 18k white gold case, stepped bezel, squared stepped bow, snap-on back, case, dial and movement signed.
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Diameter: 51 mm
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Signed: Patek Philippe Genève
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Accompanied by certificate of origin and an Extract from the Archives confirming manufacture in 1973 and sale on December 12^th 1989, chain and presentation case.

This watch may represent one of only two models of this reference in white gold. At the present time, the whereabouts of a second example is publicly unknown.

Bearing a full digital display of day, month and date held within a single aperture, the dial of this watch is an especially rare Patek Philippe design; the majority of perpetual calendar pocket watches by Patek Philippe were made with subsidiary dial indications. The ‘single aperture’ dial design enhances the clarity and ease of reading the date display and is of a type more commonly associated with wristwatches. With the sharp, clear lines of the case, the overall effect emphasises the watch’s purpose as a highly accurate timekeeper.   

The case was made by Antoine Gerlach.

A very similar watch is illustrated in Huber, M., and Banbery, A., Patek Philippe, 1982, p.228 and Patek Philippe Museum by Patek Philippe 2014 edition, volume 1 p. 386-387.