Swiss silver lever watch with temperature indicator Circa 1870

Silver open faced lever with regulator dial attributed to Sylvain Mairet
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A Swiss silver open faced pocket watch with regulator dial and temperature indicator in Réaumur, circa 1870. Bridge movement with screwed compensation balance. Case engraved to the back, blank cartouche, presentation engraving to the inside. White, enamel dial with Roman and Arabic numerals, three dials for the time and one dial for the temperature indicator.
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Diameter: 50 mm
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Weight: 87 g
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Signed: No name
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Pocket watches with thermometer have been around since the 18th century and most of the big brands have included this complication in their range: Leroy et Fils and Emery, Breguet and Jürgensen as well as Roy and Patek Philippe. Every one of them has created watches with glass or metal thermometers at one point. The design of the cases and dials was correspondingly diverse. Fritz von Osterhausen describes the dial of this timepiece.
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Chronometer maker Sylvain Mairet (1805 – 1890) is thought to have found a particularly elegant design for a dial with a thermometer around 1840. In any case, this design is attributed to Mairet, even if no example with his signature is available. It is a regulator dial like those by Jürgensen/Houriet with individual dials for hours and for minutes in the centre, subsidiary seconds at 6 o’clock and a large semicircular temperature scale extending from one side to the other around 12 o‘clock. The elegance of the watch face is emphasised by a very fine and narrow bezel. Several Swiss makers have adopted this sophisticated design for their dials, such as Robert Brandt in La Chaux-de-Fonds or Laederich Frères in St. Imier. (Temperaturfühler für die Tasche, Klassik Uhren, 6 / 2004, p. 12ff).
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The Réaumur scale is a temperature scale proposed by French natural scientist René- Antoine Ferchault de Réaumur in 1730, where the freezing and boiling points of water are set at 0 and 80 degrees respectively.