Tachometer, Victometer Centrifugal, Type B, US Navy 1920s

This is a WWI or Post WWI-vintage aircraft tachometer used by the US Navy, Type B Victometer made by the Jos W Jones Co.  Can be seen on the Spirit of St.Louis instrument panel, see photo.  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.