Unique French diamond custom made ring watch Circa 1777

Diamond ring watch by Joseph-Simon Cousin
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An exceptional, unique and important French Louis XVI miniature calendar ring set with diamonds, circa 1777. With four hands for the indication of the date, days of the week, months of the year, signs of the zodiac and moon phases with a lunar calendar. Accompanied by the original shagreen covered fitted presentation box and the original manuscript description presumably in Cousin’s handwriting.
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An 18 carat gold body and reeded shank, the border, shoulders and hinged oval bezel are set with rose cut diamonds, the concealed catch is released by depressing a diamond on the right shoulder and another diamond at 10 sets the calendar. Oval white enamel dial by Joseph Coteau with concentric indications for the date, days of the week and the months with their number of days, outer signs of the zodiac, the outermost border decorated with polychrome flowers and trophies, an aperture for the moon phase with a lunar calendar on the periphery, and two steel hands and two gold hands from the center. An oval, gilt brass movement. Dial signed Cousin Invenit et Ft., dial reverse signed Coteau Ft. 1777.
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Dimensions: 21 x 19 mm
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Signed: Joseph-Simon Cousin Paris
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The dial is chipped and has hairlines.
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This unique ring with a miniature calendar from the reign of Louis XVI represents a very early example of a miniaturized calendar, some 35 years before Étienne Tavernier was making similar mechanisms for watch keys. The survival of the fitted box and original manuscript description is nothing short of miraculous. In 1777, this ring would have been seen as a marvellous curiosity and extremely expensive. The sumptuous diamond setting was intended to show it off to maximum effect and it is very likely to have been made with a member of the Royal family in mind.

The making of the ring was a collaboration between watchmaker Joseph-Simon Cousin who was watchmaker to the younger brother of Louis XVI, the Comte d’Artois (later Charles X) and Joseph Coteau, the most eminent French enameler of the 18th century. Signed and dated dials by Coteau are extremely rare, the fact that the dial of this ring is signed and dated further illustrates its importance and that Coteau wished to be known as the maker of this dial for posterity.

In his handwritten description, Cousin describes the ring as unique and therefore as far as he knew, nothing like it had been made before. It is ingeniously conceived and beautifully made, the hidden release catch to open the bezel is activated by pressing one of the diamonds and the hand setting is achieved the same way, by pressing another diamond in the band. All four hands for the calendar indications are mounted from the center arbour for the elegance of design. Both Louis XVI and his brother, the Comte d’Artois were very interested in horology. It is certainly quite possible that as Cousin’s main patron, the Comte d’Artois, was intended to be the recipient of such an exquisite and exceptional curiosity, Cousin knew that whoever wore this ring would attract the admiration and envy of many at court.