Turn & Bank Indicator, AN5820-1 WWII US Army Air Force
The pneumatically operated, gyroscopic AN5820-1 Turn & Bank Indicator, Bendix part number 1721-2U-A2, was used across all aircraft of the US Army Air Force during WWII, such as heavy bombers B-17 and B-24, medium bombers B-25 and B-26, as well as fighters P-38, P-39, P-40, P-47, and P-51, according to the US Army Air Force's Interchangeability Cross Reference Chart dated Feb 1945. In aircraft without a central vacuum filtration system, it would have the small air filter AN-5821-1 attached to its rear top port.
It is in fine condition given its age. This indicator has a service label stamped April 1945 on its rear. The dial markings are clear and the glass, floating ball chamber, and case are intact. See photos. Measures 3.25 inches diameter and ~5 inches deep.