Swiss chronograph watch with tachometer and registers Circa 1945

Gold open faced lever pocket watch by Patek Philippe & Co.
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A Swiss yellow gold open faced chronograph watch with vertical registers, retailed by Serpico Y Laino, circa 1945. The watch features a rhodium plated calibre 13 130 manual movement with a gold wheel train, 23 jewels, eight adjustments, lever escapement, monometallic compensation balance with gold temperature screws, and a blued steel Breguet balance spring. It has a silvered dial with applied yellow gold Arabic and baton numerals, an inner track for minute and fifths of a second division, an outer tachometer scale, a subsidiary dial for the seconds, a 30 minute register, and gold baton hands.
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The polished 18 carat yellow gold case includes a snap on case back and buttons at 11 and 1 for the chronograph functions. The caseback is marked S&L for Serpico y Laino. Both the case and dial are signed by the retailer and maker, and the movement is signed by the maker. It comes with a Patek Philippe Extract from the Archives and an associated 18k yellow gold chain.
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Diameter: 46 mm
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Signed: Patek Philippe & Co. Genève
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The Patek Philippe reference 685, introduced in the late 1930s, was produced in very limited quantities until around 1950. This particular lot showcases highly esteemed features prized by Patek Philippe enthusiasts, including a Sterns Frères dial, a distinctive Wenger case, and a rare movement calibre. The calibre 13 130 was incorporated into fewer than 200 pocket watches during its production. 
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To our knowledge, only 30 pieces exist in yellow gold. Among these, a select few are believed to be doublesigned by the renowned Caracas retailer, Serpico y Laino, including this watch.
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The case is in good overall condition, showing surface wear and scuffing appropriate for its age, with some areas displaying patina. There is a small nick on the bezel at the 1 o’clock position. The case back and bands have more noticeable scuffs, along with scuffing and scratches on the bow. The bottom of the case band has a small indentation. The dial exhibits some patina on the hands and applied indexes and appears to have been cleaned. There are minor surface marks and light dust present. The chronograph function is not operating correctly, but the movement is running.