Double dial cylinder watch with equation of time and calendar dials by David Pons

This splendid example of an 'equation of time' watch has two dials. The main dial, on the front, shows the hours and minutes in the normal way. It also has a polychrome enamel border decorated with the signs of the zodiac and a scale with the months and the number of days in each. There are two minute hands on the watch. The gold hands on the main dial show true solar hours and minutes, with the uppermost hand showing mean solar minutes. The steel hand turns once per year to show the date. In the middle, the inscription 'Solis ad instar' indicates that the dial shows the time according to the sun.The white enamel dial on the back shows the days of the month and mean solar hours and minutes. Both dials, signed 'Coteau' on the reverse, were made by Joseph Coteau, one of the most accomplished dial enamellers of eighteenth century Paris. The movement is signed 'David Pons' and the fact that the regulation dial for altering the rate of the watch is inscribed 'Avanza' and 'Ritarda' suggests that the watch was made for an Italian customer.The movement, with fusee and cylinder escapement with a plain brass three-arm balance, is housed in a gold case, glazed back and front to reveal the dials. Inside, the case is punched with marks used in Paris between 1768 and 1774 and also has the makers mark 'JAA', probably that of Jean Antoine Alazard of Paris.