Hartmann & Braun
Temperature Indicator, Electrical, 160deg C, Luftwaffe Fl.20358 FW190
Here is a WWII-era electrical Temperature Indicator used in aircraft of the German Luftwaffe, measuring temperature from-10 deg C to 160 deg C. Likely used to measure cylinder head or oil temperature, the flexibility facilitated by the adjustable limit pointers. It is labeled Fl.20358, and was made by Hartmann & Braun. According to references on the internet, this instrument appeared in Luftwaffe aircraft Focke-Wulf 190 D-9, FW Ta 152, Dornier Do 335, and Junkers Ju 388.
It appears that the lens can be removed and the upper and lower operating limit indicators can be set by sliding the triangular pointers along the scale (we have not attempted this in order to preserve the artifact).
Measures ~1.8 inches diameter and ~2 inches deep. In reasonable condition given its age.