Rare Swiss gold watch with 36 hour power reserve Circa 1925

Gold watch with 36 hour power reserve by Patek Philippe
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A fine and very rare Swiss gold 36 hour power reserve open faced keyless observatory chronometer, circa 1925.
Counterpoise lever escapement movement, twice stamped with the seal of Geneva, cut bimetallic compensation balance with peripheral timing screws, wolf’s tooth winding mechanism, swan neck regulation system, 18k engraved cuvette, silvered matte dial, applied gold Roman numerals, engraved and enamelled power reserve indication, subsidiary seconds, outer circular grained minute track, 18k yellow gold bassine case, dial, cuvette and movement signed, case stamped.
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Diameter: 50.5 mm
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Signed: Patek, Philippe & Co Geneva Switzerland
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With an Extract from the Archives confirming manufacture in 1925. 

In 1844 Patek met the French watchmaker Jean-Adrien Philippe, who demonstrated his new invention: the first watch without a wind-up key. Patek and Philippe decided to work together from 1845 and in 1851 their company Patek Philippe and Cie was founded. In 1901 the name was officially Ancienne Manufacture d’Horlogerie Patek Philippe and Cie, S.A.
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The company has 70 patents and produces the entire clockwork in-house.
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Patek Philippe (1839), together with Audemars Piguet (1875), Vacheron Constantin (1755) and A. Lange und Sohne (1845), is considered to be “the big four” in the watchmaking world. The very luxurious timepieces are of high quality and therefore often raise record amounts at auctions. A pocket watch produced in 1933 was sold for 11 million in 1999 at an auction of Sotheby’s. A world record at that time. On 11 November 2014 it was auctioned again and this time it was sold for 19 million euros.