Jos W Jones
Tachometer, Victometer Centrifugal, 1920s
This is a WWI or Post WWI-vintage aircraft or laboratory tachometer "Victometer" made by the Jos W Jones Co. This is a centrifugal tachometer: as the rotation of the engine shaft rotates a cable attached to the case, flyweights rotate around an internal axis. The weights move outwardly due to centrifugal force, which pull a brace attached to the spring-loaded pointer. As the brace is pulled by the centrifugal force of the weights, the pointer is rotated clockwise, thus indicating RPMs. Very cool.
This specimen appears to have been used as a test fixture, given the rubberized interface tool affixed to the spindle. Measures ~4.24 inches diameter and ~2.25 inches deep.