Tachometer, Luftwaffe Fl20569 Drehzahl-Ladedruckmesser
Here is a fine specimen of the WWII-era Drehzahl-Ladedruckmesser, a combination Tachometer and turbocharger Boost Pressure indicator, Fl20569, as used in two advanced, late-war aircraft of the German Luftwaffe, the Do 335 and the Ju 388. This indicator displays RPM from 500 - 3600 using the small pointer along the inner scale, and turbocharger boost pressure from 0.6 - 1.8 ata (atmosphäre absolut; 1 ata =~ 1 bar) with the long pointer along the outer scale.
Two tachometers, one for each engine, were used in the Dornier Do 335 Pfeil ("Arrow") fighter and the Junkers Ju 388 Störtebeker. See photo of the cockpit of the Do 335 showing the location of its two tachometers. According to Wikipedia:
The indicator is experienced but in good shape for its age. The glass and case are intact. The glass could be cleaned by rotating and removing the retaining ring. Measures 3.5 inches square by ~ 6 inches long.