Brake Pressure, Dual, 3000 PSI
This is a Dual Brake Pressure indicator as used in various aircraft of the British RAF and Canadian RCAF. It measures the hydraulic pressure in the supply lines to both port and starboard undercarriage up to 3000 PSI.
The top right and lower left mounts are damaged, see photos, but otherwise the face and glass of the indicator are intact. Measures 3 inches diameter and ~2 inches deep.