Short answer
Fake Atmos hour is not a phrase Jaeger-LeCoultre uses. It shows up in two searches. One is about counterfeit Jaeger-LeCoultre Atmos clocks. The other is about how the Atmos keeps time. The Atmos is a clock, not a wristwatch. It has no battery, no winding crown and no hourly winding cycle. A sealed gas capsule drives the mainspring. The torsion pendulum turns 360 degrees once per minute, which is 60 turns per hour.
What the Atmos clock is
Jean-Leon Reutter filed the first Atmos patent in France in 1928. Jaeger-LeCoultre took over the design and has built the clock in Le Sentier, Switzerland, since the 1930s. The movement runs on air. A metal bellows filled with gas expands and contracts as room temperature moves. Each 1 degree Celsius of change winds the mainspring enough for about 48 hours of running. Owners set the clock on a shelf and it runs for years.
Where the word hour comes from
No part of a standard Atmos is measured in hours except the time display. There is no hour-based power reserve and no hourly reminder. Two numbers get mixed up in search results:
- Pendulum rotation: 360 degrees per minute, 60 turns per hour.
- Gas winding: about 48 hours of reserve for each 1 degree Celsius of temperature change.
The hour hand is set from the back of the case with a knurled wheel. Hands move forward. Most owner guides warn against forcing them backward.
Signs of a counterfeit Atmos
- Power source. A genuine Atmos has no battery compartment. A case with a battery door or a quartz movement is not an Atmos.
- Gas capsule. Look for a sealed bellows, a chain and a ratchet pawl that winds the mainspring. Copies mold the shape in plastic.
- Dial print. Genuine dials carry the Jaeger-LeCoultre name, the word Atmos in script, and a small model name. Fuzzy print or the wrong typeface is a signal.
- Serial and reference. Genuine clocks have a serial stamped on the movement and a reference on the case. Jaeger-LeCoultre can check a serial against its records.
- Finish. Base plates are rhodium or gilt finished. Screws are polished. Movement plates carry a JLC caliber number.
- Price. New Atmos clocks start near 7,000 US dollars. Limited pieces pass 100,000 US dollars at auction. A 200 dollar Atmos from a marketplace is a spring clock in a glass case.
What a replica Atmos contains
Listings for Atmos replica clocks ship one of two things: a quartz clock with a rotating ornament, or a 31-day spring clock. Both need a battery or winding. Neither reacts to temperature. No other manufacturer sells a temperature-wound clock under the Atmos name. The Atmos word is a live trademark of Jaeger-LeCoultre.
Checks before you pay
- Ask for a photo of the movement, not the dial.
- Ask for a video of the pendulum. A genuine torsion pendulum turns about once per minute.
- Ask if the clock ran for a month with no battery and no winding. A real Atmos will. A copy will not.
- Ask for the serial and reference numbers, then verify them with Jaeger-LeCoultre.
Cost of being wrong
A counterfeit Atmos has no service path. Jaeger-LeCoultre restores genuine clocks and keeps parts for older calibers. A quartz copy goes to a general repair shop, or to the trash. If the seller cannot show the movement or the serial, treat the listing as a copy.