Tachometer, Sensitive, Electric, US Navy, 88-I-2385-100 AD Skyraider P-2 Neptune but perhaps not surprising for

but perhaps not surprising for an artifact of its age

and the left hand switch reverses course 180 degrees

part number 1784163-901

vs a more concentrated drop over a specific site such as a ball bearing factory

In addition to its reliability

Tachometer, Sensitive, Electric, US Navy, 88-I-2385-100 AD Skyraider P-2 Neptune but perhaps not surprising forThis is a 1950's era single engine, electrical, aircraft tachometer made by General Electric under contract for the US Navy, part number 8DJ57GAB, FSSC number 88 I 2385 100. This appears to be the type used in the Douglas Skyraider attack aircraft, models AD 2 and AD 3 (see photo of instrument panel from its flight manual dated 1950 showing the location of the tachometer). RPM in 100's is indicated on the outer scale. RPM in 1000's is indicated in the