Exhaust Pressure Differential Gauge, Fl20515, Luftwaffe F8F Here is an interesting video

Here is an interesting video describing how the K-13 functioned

This is a dual DC Ammeter

The lever assembly is mounted on a 8"x10" black pressed-wood display

Our Google Translate app interpreted the date on the label as Showa 11

evidence of a manufacturing year of 1944

Exhaust Pressure Differential Gauge, Fl20515, Luftwaffe F8F Here is an interesting videoThis is a WWII era Exhaust Differential Pressure Gauge, Fl20515, as used in aircraft of the German Luftwaffe such as jet fighters Me 262 Schwalbe (see illustration of Me 262 cockpit panel showing the location of 2 indicators) and He 162 Volksjger. The gauge indicates pressure differential up to 1 kg per square cm. The indicator is in very good condition given its age. Measures ~2. 25 inches diameter and ~3 inches deep.