Air Position Indicator System Computer 12580-3-B & Manual T.O. 5N-3-1-31 PZL The case is ~5x5 inches

The case is ~5x5 inches and ~11 inches tall

as used in the US Army Air Force's Boeing B-29 Superfortress (see photo of B-29 Flight Engineer's instrument panel with a red dot showing instrument location)

the gauge always shows the amount of fuel

This model indicated vertical airspeed from 0-6

The metal seal is in place in the lower right of the case

Air Position Indicator System Computer 12580-3-B & Manual T.O. 5N-3-1-31 PZL The case is ~5x5 inchesThe Air Position Indicator System was an advanced navigational system introduced during WWII in later versions of the Boeing B 29 Superfortress Bomber by the US Army Air Force, including the Enola Gay (see API on navigator's panel). This electro mechanical system computed positions based on a series of dead reckoning inputs. The system maintained a continuous indication of the latitude and the longitude of the air position at any instant, as well as