What "replica Atmos hour" means
The phrase points to two things: copies of the Atmos clock, and the hour display on that clock. The Atmos is a table clock made by Jaeger-LeCoultre. It is not a wristwatch. It has no crown, no battery and no winding key. Jean-Leon Reutter built the first version in 1928 in Neuchatel. Jaeger-LeCoultre bought the rights in 1936 and has made the clock since.
How the original runs
A sealed capsule holds a gas mixture. The gas expands and contracts when the room temperature changes. That motion winds the mainspring through a chain and a ratchet. Jaeger-LeCoultre states that a temperature change of 1 degree Celsius gives about 48 hours of running power. A torsion pendulum replaces the balance wheel. It rotates one full turn per minute, far slower than a wristwatch balance. Power draw is small enough that the clock can run for years without human input.
Rate is not fixed. The clock reacts to the room, so accuracy shifts with temperature swings.
The hour display
Most Atmos clocks show hours and minutes on a 12-hour dial. Some early Reutter-period models used a 24-hour dial. Buyers who search for "Atmos hour" may be looking for that dial layout or for a clock with an hour-only display.
What copies use
- Battery quartz movement. Hour and minute hands driven by a cell, not by a gas capsule.
- Decorative pendulum. The disc turns, but nothing winds a spring.
- Case in brass, gold-plated zinc alloy or steel. Dome in acrylic or glass.
- Printed or applied numerals. No serial number, no Jaeger-LeCoultre marking on the movement.
A working copy of the gas capsule system is rare. The capsule, the chain and the low-torque escapement need tight tolerances, and a quartz substitute costs far less to build.
Checks on a clock sold as Atmos style
- Look for a winding hole or a battery door. A real Atmos has neither.
- Time the pendulum. One turn per minute on the original.
- Check the back of the case for a capsule and a serial number.
- Ask for movement photos. Copies show a quartz caliber in a plastic holder.
Price and legal status
Listing prices for copies move with the seller and the finish. Any single figure quoted online is a snapshot, so verify at the point of sale. In the United States, trafficking in goods that carry a counterfeit registered trademark is a federal offense under 18 U.S.C. 2320, and Customs and Border Protection can seize shipments. Patents on the 1928 mechanism have expired. The Jaeger-LeCoultre name and logos remain trademarks and have no expiry date.
Service and parts
Original Atmos clocks need a watchmaker who knows the torsion movement. Parts for the gas capsule are not sold at retail. Copies use standard quartz calibers, so a jeweler can swap a cell or a module. Resale value on a copy sits near the cost of the case.