Model 528-8 in gilt-brass with perpetual motion. Serial number 558403, dating it in the early 1980’s. Atmos clocks are known as perpetual motion clocks, as they require no winding. An aneroid chamber mounted on the back of the movement contains a mixture of liquid and gas which expands and contracts with movements in temperature, and this motion winds the mainspring. Even a one degree change in temperature is sufficient to wind the clock for 2 days’ duration.The silent operation and the torsion pendulum’s slow oscillations make these clocks very restful to watch. All is in exceptionally good order and in perfect working condition.