Month-Going Skeleton Table Regulator with Remontoire, Equation of Time, and Calendar

An extraordinary early skeleton clock with precision complications, such as solar and mean time and remontoire. It is a masterpiece of horological technology.

The top enamel dial has finely pierced gilt hands for mean time hours and minutes, steel solar time hand and center seconds. The motion work is visible through the center. The silvered annual calendar dial below has star crossings. A further dial below displays the state-of-wind and is engraved remonte à droite with symbols for the days of the week.

A remontoire is a high precision device whereby the main source of power periodically winds up a spring to overcome the variation in driving force that occurs between a fully wound spring and one that is almost run down. By providing constant force, accuracy is greatly improved.

The movement has a large spring barrel driving a three-wheel train for the re-winding of the remointoire. The coup perdu* pinwheel escapement is driven by a small weight, with a counterweight, suspended from a very fine steel chain and rewound automatically at short intervals. The inverted Y-shaped frame is mounted on the back plate with a steel and brass compensation gridirion acting on the upper suspension block. The pendulum has a large lenticular brass bob and steel rod, the whole raised on adjustable feet.

*A coup perdu (“lost beat”) escapement converts a 1/2 second beating pendulum to directly control an escape wheel at the rate of a one second pendulum, so only every other beat is registered by the escape wheel. Hence the 'lost beat' name. The escape tooth passes without advancing the wheel. This design was invented by Jean-Baptiste Dutertre, France, circa 1720 and was used by prominent French makers.