Taken from: Mike's Atmos Overhaul Class Notes – Supplemental Most of the information contained in this article has been obtained from the book, “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 we refer to these at 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" or “Brevets J. L. Reutter S. G. D. G.” (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 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 calibers and 529 calibers. Serial numbers 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, so please don't get caught up in the “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 numbers start at 70,000 and went right up 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. The following is a break down of the movement caliber numbers and the corresponding range of the Atmos serial numbers: Caliber # Serial # Range 550 Special 50th Anniversary 540 600,000 and up 526-5 & 528-6 & 528-8 107,000 - 599,999 526-5 & 528-6 & 529 & 532 70,000 - 106,999 519 & 522 & 529 & 532 60,000 - 69,999 Atmos II & 519 & 529 4,000 - 59,999 The serial numbers are located on top of the movement next to the fast-slow adjustment. On some early caliber 519's and the Atmos II’s the serial number is located on the bottom of the movement and you can see it through the front of the case. The following Acrobat file contains some of the Atmos clocks I have work on, listed by serial number. After the serial number is the date that was found on the bellows. The bellows were made in batches, so there is some duplication but more than enough information to date your specific Atmos to within a month or so. All I ask is that you reference where you obtained this information if you use it anywhere on the Web including sales or auctions. http://www.atmosman.com/pdf/$atmos.pdf This file contains is the serial #'s of over five hundred Atmos clocks that I have repaired that still have had the original bellow intact. The serial numbers are located on top of the movement next to the fast-slow adjustment. On some early caliber 519's and the Atmos II's the serial number is located on the bottom of the movement and you can see it through the front of the case. The caliber's from the 522 to the Atmos' made today are stamped, with the particular caliber #, on the bottom of the case. The Atmos II and caliber 519 were not stamped on the bottom and are nearly identical. You can tell the difference because the Atmos II has the speed adjustment as a turn screw rather than a slide lever, which is found on the caliber 519 and all models since. A service from, E-mail address Mike@atmos-man.com Mike Murray Founder of Clocksmiths A specialist in Atmos and 400-day clock repair. Also, I overhaul most plug in electric clocks. In continuous service since 04/01/1982. Mike's Clock Clinic 1600 Maryland Avenue Myrtle Point, OR 97458-1508 541-559-1090 My Web site is located at http://www.atmosman.com/ Main FTP site is located at: http://www.home.earthlink.net/~atmosman/earthpdf.html Memberships: Clocksmiths; NAWCC N.A.W.C.C. International 400-day Clock Chapter # 168 Formally Published in Chapter 168's "Torsion Times" Former AWCI's 400-day (Anniversary) clock Bench Course Instructor!