Jaeger-LeCoultre Atmos Clocks
Atmos clocks are technical marvels. Inside each clock is a hermetically sealed capsule that contains a mixture of gas and liquid that expands as the temperature rises and contracts as it falls. This motion constantly winds the mainspring, a variation in temperature of only one degree centigrade being sufficient for two days' operation.
Every Atmos clock is made entirely by hand, and with some models, a single clock takes a month to produce. The incredible precision of the Atmos' manufacture produces clocks that have an expected service life of over 600 years.