Tachometer, Electric, Weston Type 545
Here is a WWII or pre-WWII-era electrical Tachometer measuring up to 2500 RPM, made by Weston. It is marked as being adjusted for series connection, so it may have been intended for a two seat trainer. It has two markers, yellow and red, along the dial scale that can be placed to indicate operating limits when installed. Measures 3.25 inches diameter by ~2 inches deep.