Gyrosyn Compass C-2A Sperry Master Indicator 653894-6B C-119 Boxcar USAF P-2 Neptune as appeared on the flight

as appeared on the flight engineers panel of aircraft of the US Navy such as the patrol bomber / seaplane PBM-5 Mariner (see illustration showing the location on the panel from the PBM-5 flight manual dated 1944)

Here is a WW2-vintage electrical Free Air Temperature Indicator

The US Navy Anchor logo is stamped on the back and on the face is embossed "BU AERO US NAVY" (Bureau of Aeronautics)

which existed with that name from 1918-1926 until it was renamed Air Corps US Army

Gyrosyn Compass C-2A Sperry Master Indicator 653894-6B C-119 Boxcar USAF P-2 Neptune as appeared on the flightThis is a Gyrosyn Compass Master Indicator Type C 2A made by Sperry part number 653894 6B. The Master Indicator was part of a 5 module system combining the functions of a directional indicator and a magnetic compass, introduced in the late 1940's. See the diagram of the system with an explation of its function in the photo gallery, including a diagram of this specific indicator. An illustration of its position on an instrument panel is in the photos