Gyro Horizon, Pneumatic, FL22427, Luftwaffe Wendehorizont
Here is a WW2-era German pneumatically-powered "Wendehorizont" Gyro Horizon FI.22427, made by Askania (see "Hersteller: bxx", bxx was the code for Askania). This Wendehorizont was used in aircraft of the Luftwaffe such as twin-engine night fighters Messerschmidt ME 110, 210, and 410, and bombers Junkers JU 88, Heinkel HE 111, and Heinkel HE177 Greif.
The knurled rim around the glass lens can be rotated, which cages (Fest) or releases (Los) the gyro.
Measures approx 4 inches diameter and ~7 inches deep. It is in exceptional condition given its age.