9678 A Louis XV gilt bronze mounted kingwood regulator by Coupson, Paris, case by Dubois, the silvered brass dial with Roman numerals, seconds dial and date aperture, with an outer, manual dial for the equation of time (now disconnected,) the shaped hood with gilt bronze bezel above a waisted case with lenticle or window on a tapered plinth base, stamped DUBOIS JME.
Jacques Dubois, (1694-1763,) Maitre 1742
Private Italian collection.
H: 88 ins (224 cm)
W: 22.75 ins (57.5 cm)
D: 10.75 ins (27.5 cm)
The Equation of Time complication allows the viewer to understand the variation between Solar time, as measured by exact position of the sun and Mean Solar time, the position averaged over a year. This differential could be as much as +- 14 to 16 minutes per day depending on the time of year, due to the slight elliptical motion of the earths rotation around the sun.
The outer ring is marked with months and days and when aligned at the current date, a revised minute dial shows the compensated time at that moment.