Regulator with Glass Vacuum Tank

This regulator (Movement No. 89, DRP No. 50739/100870) with Invar nickel/steel compensation pendulum no. 726 - Type J, contains the Riefler spring impulse escapement, which allows the pendulum to oscillate almost totally free of connection to the movement. Warner and Swasey Observatory of the Case Institute of Technology in Cleveland, Ohio purchased this regulator in 1906. At the time, this type of regulator was the finest and most accurate clock available. The stated precision for the Type D clock was 10 milliseconds per day, although better rates were frequently achieved.

Fewer than 15% of the regulators produced by Riefler were in glass vacuum tanks, and only a few survive today.