Short answer
Jaeger-LeCoultre does not sell a product called the "Atmos Hour." The Atmos name belongs to a clock line, not to a watch and not to an hour. Search traffic for "fake Atmos hour" lands in two places: people hunting replica Atmos clocks, and people hunting counterfeit Jaeger-LeCoultre watches. No factory sells a working copy of the Atmos movement.
What the Atmos clock is
Jean-Leon Reutter built the first Atmos in 1928. Jaeger-LeCoultre took over production in 1936 and has made the clock in Le Sentier, Switzerland since then. The movement has no battery, no cord, and no winding key.
A sealed capsule holds a gas. That gas expands and contracts with the surrounding air temperature. The capsule drives a chain that winds the mainspring. A change of one degree Celsius supplies enough energy for roughly two days of running. The torsion pendulum makes one oscillation per minute.
Why working replicas do not exist
- The capsule is a sealed vessel under pressure. A copy needs gas filling equipment and a leak test.
- The caliber holds hundreds of parts, including a chain, a torsion spring, and a regulator.
- Sales volume is low. Genuine units sell in small numbers at high prices, so a $300 copy has no market.
No known factory sells a clock that winds itself from temperature change. Any listing that claims this is either genuine or misdescribed.
What fakes do exist
- Quartz clocks in an Atmos-style case, with columns, a glass dome, and a rotating disc that imitates the pendulum.
- Electric torsion clocks from other makers, relabeled as Atmos.
- Marriages. A real Atmos movement placed in a case from a different clock.
- Redials, mismatched hands, and parts assembled from several clocks and sold as one unit.
How to check a clock sold as Atmos
- Read the back plate. Genuine clocks carry a Jaeger-LeCoultre or LeCoultre signature and a serial number.
- Look for a battery door or a power cord. Genuine units have neither.
- Time the pendulum. One full oscillation takes 60 seconds.
- Ask for service records. The maker states a service interval of about 20 years.
- Match the case, dial, and hands against catalog photos from the same decade.
Prices
Vintage Atmos clocks from the 1960s and 1970s sell at auction for about $1,000 to $4,000. Current catalog models list above $8,000. A clock described as Atmos at $400 or less is a warning sign. So is a seller who will not show the back plate or the serial number.
If you want a real one
Buy from a dealer who repairs torsion clocks, or from an auction house that prints the movement number in the lot description. Add $400 to $900 for a service if the clock has not been cleaned in 20 years. A non-running Atmos can be repaired in most cases, but a leaking gas capsule is the part that decides the cost.