Swiss astronomical world time watch with 24 world locations Circa 1790

Unsigned gold and enamel double dialled watch 
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A Swiss gold and enamel double dialled astronomical world time watch with 24 world locations and their latitude, calendar and moon phases, circa 1790. The watch features an unsigned gilded movement with verge escapement, plain cylindrical pillars and fusee and chain. It has two dials: the front dial is white enamel with black Roman numerals for 24 hour timekeeping, outer minutes, inner rings calibrated for the month with corresponding polychrome enamel painted signs of the zodiac, an inner date ring, and a central blue enamel roundel for moon phases heightened with gold stars, with a winding aperture at 3 o’clock. The second dial is white enamel with a blue chapter ring featuring Arabic numerals for 24 hour timekeeping, with the center displaying a large gold disc in the form of a blazing sun with 24 points, each engraved with a world location and its corresponding point of latitude North or South.
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The gold case has foliage engraved bezels, featuring a pendant stamped 18K and numbered 9260, along with the initials ILR and the letter F in a square cartouche.
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Diameter: 56 mm
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Signed: No name
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The movement is operational. The dials are in good overall condition and the case shows light scuffs and scratches.
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An almost identical double dialled watch can be found at the Patek Philippe Museum in Geneva. This watch is also illustrated in P. Friess’s book, The Emergence of the Portable Watch.