Gyro Horizon, Pneumatic, FL22427, Luftwaffe Wendehorizont
Here is a WW2-era German pneumatically-powered "Wendehorizont" Gyro Horizon FI.22427, made by 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. It is tight but still rotates.
Measures approx 4 inches diameter and ~7 inches deep. The glass lens is present and secure, but loose in its frame. There are a couple of small knicks in the metal dial, see photos It is in good condition given its age.