Atmos 566 is a calibre number used by Jaeger-LeCoultre for its Atmos clock. A real Atmos runs on a sealed gas capsule and a torsion pendulum. It has no battery. Copies sold as Atmos 566 use quartz or battery movements inside a case that copies the outside shape. The movement is the check that matters.
What the number 566 means
Jaeger-LeCoultre stamps calibre numbers on the movement plate inside Atmos clocks. Other Atmos calibres include 540, 560, 561 and 582. The number is not a model name. Atmos models carry names such as Classique, Transparente and du Millénaire. A listing that says Atmos 566 and shows no photo of the movement describes a case, not a clock.
How a real Atmos runs
The Atmos has no battery and no winding key. It runs on air.
- A sealed capsule holds a gas mix. The gas expands when the room warms and contracts when the room cools.
- The capsule drives a chain and ratchet that winds the mainspring.
- Jaeger-LeCoultre states that a change of 1 °C gives about 48 hours of running energy.
- The torsion pendulum has a period of about 60 seconds.
- Jean-Léon Reutter patented the design in 1928. Jaeger-LeCoultre took over production in the 1930s.
Why a fake cannot copy the mechanism
A quartz movement cannot drive a gas capsule. Copies use a battery, a small motor and a swinging weight shaped like a pendulum. That pendulum stops when the cell runs out. A gas capsule is sealed at the factory, and no aftermarket supplier sells one for a counterfeit case. This is the reason a low cost copy keeps time with a battery and a real Atmos does not.
Checks before you buy
- Ask for a photo of the movement plate. Look for the Jaeger-LeCoultre name and a calibre number.
- Ask if the clock takes a battery. A real Atmos has no battery compartment.
- Ask for a video with the base open and no cell installed. The pendulum should turn.
- Check the serial number on the base or the back. Jaeger-LeCoultre can confirm the number and the date through its archive service.
- Compare the price. Working used Atmos clocks sell for hundreds to several thousand US dollars.
Legal note
In the United States, the Lanham Act covers trademark counterfeiting. US Customs and Border Protection can seize counterfeit goods at import. A seller of a counterfeit clock can face civil claims from the trademark owner.
What is not public
Jaeger-LeCoultre does not publish a full table that links each Atmos calibre to a production year. Auction records for calibre 566 clocks are the main public source, and those records disagree on dates. Treat a stated production year as unverified until the manufacturer confirms it.