Exquisite Gold-Plated Jaeger-LeCoultre Atmos Clock. 540 Caliber Model. Comes with guarantee form from prior owner. 

Size: 7 3/4 x 6 x 9 in. 

#4239 . 

Atmos is the brand name of a mechanical torsion pendulum clock manufactured by Jaeger-LeCoultre in Switzerland which does not need to be wound manually. It gets the energy it needs to run from temperature and atmospheric pressure changes in the environment, and can run for years without human intervention. The clock is driven by a mainspring, which is wound by the expansion and contraction of liquid and gaseous ethyl chloride in an internal hermetically sealed metal bellows. The ethyl chloride vaporizes into an expansion chamber as the temperature rises, compressing a spiral spring; with a fall in temperature the gas condenses and the spiral spring expands, winding the mainspring. This motion constantly winds the mainspring. A temperature variation of only one degree in the range between 59 °F and 86 °F was calculated to provide energy for two days’ operation in an early prototype. To run the clock on this small amount of energy, everything in the Atmos must be as friction-free as possible. For timekeeping the torsion pendulum consumes less energy than an ordinary pendulum, and has a period of precisely one minute, thirty seconds to rotate one direction and thirty seconds to return to the starting position. This is thirty times slower than the seconds pendulum typically found in a longcase clock, where each swing (or half-period) takes one second. The first clock powered by changes in atmospheric pressure and temperature was invented by Cornelis Drebbel in the early 17th Century. The Beverly Clock in Dunedin, New Zealand, is still running despite never having been manually wound since its construction in 1864. The first Atmos clock was designed by Jean-Léon Reutter, an engineer in Neuchâtel, Switzerland, in 1928. This noncommercial prototype, which predated the Atmos name but is now known unofficially as Atmos 0, was driven by a mercury-in-glass expansion device. On June 1st, 1929 Compagnie Générale de Radio (CGR) in France began manufacturing the first commercial model, Atmos 1, which used a mercury and ammonia bellows power source. On July 27th, 1935 Jaeger-LeCoultre took over production of Atmos 1 while it developed a second design which used the present ethyl chloride power source. This model, later named the Atmos 2, was announced on January 15th, 1936, but problems delayed full production until mid-1939. Subsequent models were based on this design, and to date over 500,000 Atmos clocks have been produced, while Jaeger-LeCoultre remains one of the top tier watchmakers in the world.