The Jaeger-LeCoultre clock introduced in 1928 that uses pressure-sensitive gas-volume changes to keep time is the Atmos clock.
The Atmos is powered by small changes in surrounding temperature and atmospheric pressure rather than by daily winding or an electric battery. A sealed capsule containing a gas expands and contracts as conditions change. That movement winds the clock’s mainspring through a mechanical system. A temperature change of only one degree Celsius can provide enough energy for roughly two days of operation.
The mechanism is designed to consume very little energy. Its balance wheel swings slowly, and the clock’s gear train is carefully arranged to reduce friction. Because the energy source is environmental, the Atmos can run for years when properly maintained, although it is still a precision mechanical instrument.
The first commercial Atmos was developed by Jean-Léon Reutter and later manufactured by Jaeger-LeCoultre. It is a clock, not a wristwatch, and should not be confused with the brand’s Reverso or Memovox models.