USN WWII Portable Cased Tachometer

USN WWII Portable Cased Tachometer-This is made by the Jaeger Watch Company for use by the Army Air Forces (USAAF) and Navy to measure engine RPMs in aircraft, featuring clockwork mechanisms. This is contained in its original fitted case of issue.This has one extra tip for different engine types, essential for maintenance and calibration. It appears that one tip may be missing. The instruction sheet is included under the lid. This is in excellent condition.