The Atmos is a table clock by Jaeger-LeCoultre, which is driven by changes in air temperature. It has been in production since 1930, with well over 750,000 examples produced, and has become the standard gift for dignitaries visiting Switzerland, as well as to commemorate important events worldwide.
The Atmos is a mechanical table clock with rotating pendulum, where the spring is wound using the thermal expansion of a suitable liquid. With pieces from 1945, ethyl chloride, which is strongly responsive to temperature changes, is used as a liquid. This liquid exerts its power when the temperature changes in a can.
The Atmos was invented by Swiss engineer Jean-Léon Reutter in 1927 and initially marketed by his employer, GCR of France. Production was taken up by the famous Swiss firm Jaeger-LeCoultre in the mid 1930s, officially becoming their product at the end of the decade. The movement was substantially revised at this time to use ethyl chloride bellows, and this basic design would remain in production through 1983, with over 500,000 examples produced. The Atmos was redesigned that year with complications in mind, and a wide variety have been produced since.
The system of a clock that used temperature to wind the mainspring was presented by Friedrich Ritter von Lössl in 1880, and he received a patent from the German Imperial Patent Office. This concept had been conceived in the 18th century by Pierre de Rivaz, James Cox, and John Merlin, but none was successful in developing it. Swiss engineer Jean-Léon Reutter developed the first working prototype of a table clock, which draws its energy from atmospheric changes, in 1927. These initial models, now called “Atmos 0”, were patented but never produced. A production model, now called “Atmos I”, was patented in France in 1929.
Compagnie Generale de Radio (GCR) of France produced the first production clocks for Reutter starting on June 1, 1929. The company set up a department to manufacture and sell these clocks, which were now called “Atmos” to reflect the source of power. It is said that Jacques-David LeCoultre noticed one of Reutter's clocks in Paris in the early 1930s and offered to take over production in Le Sentier. By September, 1932, LeCoultre was producing movements for GCR, delivering the first of these to customers in 1933.
The original Atmos movement, known as Cal. 30“A, used a wide 59 mm main plate with a 3/4 plate shaped like an arrow pointed downward. The minute wheel was retained by a distinctive three-pointed bridge, visible below the hand pivot in models with a skeletonized dial. The torsion pendulum featured six or eight crown weights that could be adjusted to set the poise of the wheel, though some used a simpler weight with just two internal weights. Many examples also feature a temperature compensating material in the pendulum. The bellows was operated using mercury and ammonia, a volatile mixture that would be replaced in later models.
LeCoultre, GCR, and Reutter produced a few thousand examples of the Atmos I clock between 1930 and 1935. Most feature a serial number inscribed on the drum, with all of these falling below 7,000. On July 27, 1935, all production of the Atmos was transferred to LeCoultre in Switzerland, along with all stock of components and works in progress. LeCoultre would continue to produce the original Atmos for sale until their new version was perfected a few years later, though production ended in November 1936.
On January 15, 1936, LeCoultre announced the new Atmos II, which used a canister filled with ethyl chloride rather than the ammonia and mercury bellows. It would take three more years of work to deliver the first Atmos II clocks for sale, however. The Atmos II was very similar to the original Reutter model, with most parts being interchangeable, but the company (now called Jaeger-LeCoultre) would rapidly evolve the design through the 1950s.
The first Atmos II went on sale in 1939, but production was sparse through World War II. Most examples date from 1942 onward, with separate serial numbers on the main plate and bracket ranging from 6,500 up to about 25,000. These are finely decorated and typically feature applied numerals, a lift-off case, and full visibility of the movement. The pendulum generally features a series of fine inscribed lines in clusters around the outside.
Jaeger-LeCoultre introduced the Atmos III in 1950, with an update movement with index adjustment. The new Cal. 519 had a narrower 50 mm main plate, while Cal. 529 was just 45 mm across. This allowed more of the wheel train to be visible and emphasized the unique features of the Atmos. The dials were mostly open as with previous models, but with numerals only at four points. The 3 and 9 “lay down” in many examples, though this is also sometimes seen in late Atmos II and early Atmos V clocks. The pendulum now featured a series of dimples rather than the fine lines, and blued screws contrast with the gold plated and Geneva striped movement. The Atmos III was produced through 1954 with serial numbers ranging from about 25,000 to 80,900, with much overlap with other models. Jaeger-LeCoultre announced in 1952 that 50,000 Atmos models had been sold.
Another Atmos model was added in 1954. This model moved the pendulum retention knob to the movement itself, allowing a hinged door to be used in the case. The Atmos IV used Cal. 522 (with a 50 mm main plate) or 532 (45 mm) and featured a single thick line on the pendulum. These were produced for a short time that year only, with all known serial numbers in the 60,000-70,000 range. This short production run makes the Atmos IV one of the rarest full-production models. One notable difference starting with the Atmos IV was the elimination of the three-pointed bridge used to hold the minute wheel. Instead, the minute train was “flying” above the three-quarter plate in this and all future Atmos models.
In 1955, Jaeger-LeCoultre introduced the Atmos V, based on a larger order for the American market. It used Cal. 526, an evolution of Cal. 522 with the flying minute wheels, narrow 45 mm main plate, and pendulum lock on the movement. Most of these feature a door rather than a lift-off case, and most also use a pendulum with sets of three thick lines inscribed around it. The Atmos V would remain in production through 1982, with hundreds of thousands sold. Serial numbers range from 70,000 to 550,000, though production ran alongside many other models.
Also available from 1959 through 1982 are the Atmos VI and VII (with Cal. 528) and VIII (with Cal. 528/1). The major difference being the cabinet, with a lift-off design, hinged door, or push door, respectively. These are very similar to the Atmos V but with changes to the movement, plates, and brackets, as well as a return to the pendulum lock under the case. Their serial numbers are similar to the Atmos V, ranging from 100,000 to 599,000. One notable model was the Atmos Moderne, a radical redesign by Luigi Colani produced in 1974 and 1975. In 1979, Jaeger-LeCoultre celebrated the sale of their 500,000th Atmos Clock. The company also issued a special Jubilee model with a novel movement, Cal. 550, limited to 1,500 pieces. This would be reissued as the Prestige with Cal. 551 shortly after.
Jaeger-LeCoultre celebrated its 150th anniversary in 1983 with a number of redesigned and commemorative products. Although the company was suffering financially at that time, having recently been sold to VDO Automotive, management re-invested in mechanical products and used the historic Reverso and Atmos to emphasize their history. For the first time, the Atmos movement was completely redesigned, with production of the descendants of Reutter's original movement halted.
The new Cal. 540 was radically different, with the main and three-quarters plates slimmed to a “coke bottle” shape somewhat reminiscent of the company's 8-day clocks. The movement and brackets were placed inside the diameter of the dial, leaving the pendulum alone below, hanging from a single tube, with a pendulum retention lever attached. Most feature three or four round legs around the pendulum, though some hang from the top of the case. The most important change was invisible at the time The barrel and wheel train was modified to turn with the phase of the moon, enabling future complicated calendar models.
Production of the Cal. 540 models appears to have started in July, 1983, with serial numbers of 600,000 and up. A limited-edition re-edition of the original Reutter model, with a hand-blown glass dome and crown weights on the pendulum, is especially collectible.
This new movement was designed for complications, and Jaeger-LeCoultre quickly began offering variations. In the 1990s, the company created a perpetual calendar version that could count to the year 3,000. One, without hour and minute hands, was laid inside the foundation of the new manufacture in Le Sentier, and others were offered in limited production to the public. A moon phase indicator is another popular complication in Atmos clocks of the 2000s, and the company also added date and astronomical complications.
Cal. 540 was redesigned in the 2000s, becoming Cal. 560. Most of the other models were phased out at this time, in favor of new standard offerings that remain in production as of 2020 The Atmos Classique (Cal. 560) and Classique Phases De Lune (Cal. 562), and suspended Atmos Transparente (Cal. 563) and Transparente Phases De Lune (Cal. 564).
The ethyl chloride is enclosed in a metal housing, which thanks to its bellows shape acts as an expansion chamber. When the temperature rises, the ethyl chloride gas expands. The chamber expands like an accordion and presses together a spring, which acts as a counterweight and is fully compressed at 27° Celsius. In this procedure, a small chain rolls around a small drum. Another small spring ensures the pull. With decreasing temperature, the chain unwinds again, the drum snaps and thereby drives the shaft of the drive spring. This spring is wound and thus saves the necessary drive energy. The precise calculation of the ratios makes it possible to keep the number of gears as low as possible to reduce the friction. The 240-gram balance wheel is actually a torsion pendulum and hangs on a thin Elinvar wire. Therefore it needs a hundred times less energy than a wristwatch! Thanks to this constant energy the exact rate of the Atmos is guaranteed.
The Atmos has become one of the great successes of Jaeger-LeCoultre. Especially in the US, many of these watches were sold. 1978 the number of produced models already exceeded the figure of 500,000. Meanwhile, there are a number of variants, including the Atmos 3000, which displays not only hours and minutes, but also the moon phase, or the luxury version “Joaillerie”, whose prismatic case is made entirely of crystal glass. With the limited model “Régulateur” the display is based on the regulator principle and the hours and minutes are shown on separate dials made of solid silver.
A rare Atmos is the Marina from the 1960s, which features white or black enamel panels with fish and sea plants behind plexiglass panels. The company also produced an unusual Atmos clock for Gruen at that time, with a wooden case with arched windows.
In 1983, Jaeger-LeCoultre released a special 150th Anniversary model under a domed crystal. This celebrated the anniversary of the founding of the LeCoultre manufacture. An Atmos Jewellery model appeared in 1992 with lapis-lazuli feet and inlaid dial weighing more than 10 kg. In 1996, an Atlantis 2000 Atmos was laid in the foundation of the Jaeger-LeCoultre factory in Le Sentier. This model featured a triangle glass case with three large conical legs as well as a helical dial showing the years from 1996 through 2496. Another special edition Atmos in 2010 was said to be a re-edition of the 1930 Reutter, though the design of the Atmos Réédition 1930 is quite updated.
Jaeger-LeCoultre celebrated the 75th anniversary of the Atmos in 2003 with the Atmos Mystérieuse in a crystal case and made of gold, onyx, and diamonds. 75 were produced, with a list price of $1.5 million.
Since the 1970s, Jaeger-LeCoultre has collaborated with famous designers to create special Atmos clocks. These are much in demand today, commanding far higher prices than the ordinary brass Atmos clocks. The first such collaboration came in 1973 when industrial designer Luigi Colani created the “Atmos Moderne”, a radical cube-shaped case with curved glass windows and a cloverleaf-shaped dial. This model is often referred to as the “Paco Rabanne”, as that designer had created a steel dress in 1966 and some thought Colani's design was similar. The cover is hinged to the chassis in a way that resembles a helmet or Colani's automobile designs. The Atmos Moderne was produced from 1973 to 1975 in limited numbers and uses Cal. 528/1.
Jaeger-LeCoultre celebrated the year 2000 with a special Atmos model, the Marqueterie du Millénaire which came with a 1,000 year calendar with month and moon phase display. This was cased in an Art Nouveau style wood cabinet with marquetry of the works of painter Alphonse Mucha executed by Philippe Monti and Jérôme Boutteçon. It used Cal. 555. This was limited to 25 examples, but the same movement was offered as the Atmos du Millénaire Atlantis in a larger run of 1,200 examples.
The next special edition Atmos came from Hermès and features a spherical crystal case with bubbles produced by Alsace glassmaker, Les Cristalleries de Saint-Louis. The Atmos Hermès Clock uses Cal. 560a and 176 examples were produced in 2013.
Two years later, a special Atmos was another with a marquetry cabinet by Maonia of Paris. 2015's Marqueterie Céleste featured straw marquetry and precious minerals with an astronomical them. The moon phase indicator uses iridescent mother of pearl on a lapis lazuli sky. Cal. 582 features a regulator-style display of hours and minutes as well as a 24 hour and month display and perpetual calendar accurate to 3,861 years.
Jaeger-LeCoultre collaborated with Marc Newson on the Atmos 561 in 2008 and the Atmos 566 in 2009. The earlier model features Cal. 561 suspended in a rounded rectangular crystal case with a single round foot. The Atmos Cal. 566 is contained in a similar case of Baccarat crystal but with three short legs. This movement adds the equation of time and was available in blue or transparent in 18 or 48 pieces, respectively. In 2020, Jaeger-LeCoultre again collaborated with Newson, this time with the Atmos 568. It is similar to the 566 but the movement and display are quite different.
Atmos clocks are differentiated by their case and their calibre or movement. Most use sequential serial numbers but these are mixed across models. There are seven different pendulum designs. Note that some parts are interchangeable and are mixed between caibres, especially for early Atmos clocks. All models prior to 1983 are based on the original Reutter design, while all after this date are based on the new Cal. 540.