Valve, Air Vacuum Regulating AN5828-2, US Navy R88-V-85X Instruments

This is a WWII-era pneumatic Valve, Air Vacuum Regulating, made by Schwien, part number 2550, as used in aircraft of the US Army Air Force and US Navy. This valve was used to regulate the vacuum pressure between its source (either an externally-mounted venturi tube, or an internal engine-driven compressor) and the system of pneumatically-powered flight instruments, such as the Gyro Horizon, Directional Gyro, and the Turn & Bank Indicators. Accuracy of these instruments depended upon the proper setting and functioning of this regulator valve. 

See the diagram of the placement of this valve in the TBM Avenger from its Erection and Maintenance Manual.

This particular instrument is labeled for use in US Navy aircraft. The last digit of the US Navy Stock Number R88-V-85? is illegible on the label.  Measures ~ 3.5 inches diameter and ~2 inches tall.