Exhaust Pressure Differential Gauge, Fl20515, Luftwaffe
This 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 Volksjäger. 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.