LeCoultre Atmos clocks have been available since 1939 and continue to intrigue collectors in retail and secondary markets. The quality clocks were invented by Jean-Leon Reutter of France in 1927, but production of the Atmos II didn't take place until 1939. The date a LeCoultre Atmos clock was made can help you determine its value. A serial number can be used to date a vintage LeCoultre Atmos clock, and a repair technician may locate a date on a clock's bellows -- the bowl shape on the back that acts as a motor. Each clock is sealed and works on changes in temperature and mercury vials.
Determine whether or not the LeCoultre Atmos clock functions and keep accurate time. The clock has a leveling tool on its bottom to keep it level for accurate operation. It requires no batteries and no winding. A working LeCoultre Atmos clock is more valuable than one that doesn't work.
Locate the serial number near the fast-slow adjustment or on the bottom of the movement visible through the case. Compare the serial number with known serial numbers and years of production. Numbers up to 6,500 were used for clocks made in 1940 and earlier. Serial numbers from 6,500 to 24,999 were used in the 1940s. Serial numbers from 25,000 to 126,999 were used for 1950s' LeCoultre Atmos clocks, and the 1960s' Atmos numbers start at 127,000 and run through 299,999. The 1970s' serial numbers start at 300,000 and are sequential through 519,999. The 1980s' serial numbers start at 520,000 and stop about 649,999. Clocks made in the 1990s have a serial number in the 650,000 to 704,000 range.
Establish the age of the clock by its serial number. As a general rule, older clocks are more valuable than newer models. Collectors want to know the serial number and age of a LeCoultre Atmos clock.
Examine the clock for damage. Check for discoloration of the brass or scratches on the glass. Any damage to the clock reduces its value on the secondary market.
Compare recent sales of the specific LeCoultre Atmos clock, reading carefully each sold clock's condition and operation as well as the market for the sale. Some sales information is available on the Internet, and other information may be available in trade magazines and books. Older LeCoultre Atmos clocks without significant damage and in operating condition sell for $500 and $800, as of 2011.