In 1928 a Neuchatel engineer called Jean-Leon Reutter built a clock driven quite literally by air. But it took the Jaeger-LeCoultre workshop a few more years to convert this idea into a technical form that could be patented. And to perfect it to such a degree that the Atmos practically achieved perpetual motion. In 1936 production of the Atmos began.
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The technical principle is a beguiling one: inside a hermetically sealed capsule is a mixture of gas and liquid (ethyl chloride) which expands as the temperature rises and contracts as it falls, making the capsule move like a concertina. This motion constantly winds the mainspring, a variation in temperature of only one degree in the range between 15 and 30 degrees centigrade being sufficient for two days' operation.
To convert this small amount of energy into motion, everything inside the Atmos naturally has to work as smoothly and quietly as possible. The balance, for example, executes only two torsional oscillations per minute, which is 150 times slower that the pendulum in a conventional clock. So it's not surprising that 60 million Atmos clocks together consume no more energy that one 15-watt light bulb.
All its other parts, too, are not only of the highest precision, but also practically wear-free. An Atmos can therefore expect to enjoy a service life of a good 600 years, although with today's air pollution a through cleaning is recommended about every twenty years.
Admirers of advanced technology, however, aren't the only ones who get their money's worth. Connoisseurs of elegant forms, precious materials and traditional craftsmanship, do so as well. Because every Atmos is still made entirely by hand; and with some models a single clock takes a whole month to produce. Not counting the five weeks of trial and adjustment that every Atmos has to undergo.
Only then, were the Jaeger-LeCoultre master watchmakers happy enough with the state of things to confirm it with a signature and allow another Atmos to leave the workshop. After which, many end up in the very best homes, because for decades now the world's most celebrated watch-making country has been presenting its distinguished guests with this masterpiece of Swiss artistry.
The Atmos has had the honour to be associated with great statesmen, royalty, and other renowned people including John F. Kennedy, Sir Winston Churchill, General Charles DeGaulle, and Charlie Chaplin.
The above information comes from LeCoultre catalogues and documents. The following is primarily from Living on Air - History of the Atmos Clock by Jean Lebet.
Jean-Leon Reutter, in France, designed the Atmos Clock in 1927 and this is referred too as the Atmos 0. These prototypes were never sold and never called the Atmos 0 at that time.
His clocks were driven by a "mercury in glass" expansion device which rotated a cylinder which wound the mainspring by ratchet. The mechanism operates on temperature change only. The clocks are slightly different to the later Atmos models in minor details of escapement.
On June 01, 1929, Compagnie generale de radio (CGR) created a department devoted to the manufacture and sales of the Atmos clock. Jean-Leon Reutter was appointed to manage that department. It is unclear how many were made and sold but they are referred to these as Atmos I's. Two French patents were granted for the Atmos 0 (624.595) and for the Atmos I (664.689) but that company never produced the Atmos 0. They are very nicely made and typically they have a plate saying "Reutter Brevet" (Brevet = Patent).
In September 1932 LeCoultre entered an agreement to develop movements for CGR and first deliveries were made in mid 1933 and these movements were called the 30" A calibre. Annual production of these movements was between one and two thousand for years 1933 and 1934.
On July 27, 1935, CGR agreed to transfer all production to LeCoultre and all remaining stock and work in process. LeCoultre continued to sell the Atmos I while it was developing the Atmos II, which the primary improvement was the change from an ammonia and mercury "bellows" to a canister filled with ethyl chloride.
By January 15, 1936, LeCoultre announced its "new" Atmos and they were still using the 30" A calibre movement. These "new" Atmos' were later called Atmos II's. By November of 1936 the Atmos I production was stopped completely. Problems arose and "full" production of the Atmos II did not start until mid 1939.
The next model was the Atmos III, which included the 519 caliber and 529 caliber. Serial number's for the Atmos II and Atmos III are somewhat intertwined because of LeCoultre purchasing the entire stock of CGR.
There is evidence of overlapping in all LeCoultre models; there are no "absolutes" of serial numbers and caliber numbers. The Atmos II and the Atmos III have serial numbers ranging from around 4,000 to 59,999 and production went from 1936 until late 1955.
The Atmos IV included calibers 522 and 532 and have serial numbers from 60,000 to 69,999. The important thing to know here is that this is LeCoultre's shortest full production run ever.
The Atmos V consist of the caliber 526 and the Atmos VI, VII, and VIII consists of the caliber 528 and the 528/1 represents the Atmos VIII. Serial range from 70,000 to 599,999. The important point here is that this is the last of the "genuine" Reutter design Atmos made and production stopped late in 1983.
In late 1983, LeCoultre totally resigned the Atmos and came up with the 540 caliber. They also stopped the practice of labeling the models numerically (Atmos 0 - Atmos VIII). These serial numbers start with 600,000 and is still being made today under various caliber numbers and model names.