Wheel and Flap Position Indicator, Type A-3 1942 Air Corps US Army
Here is a WWII-era Type A-3 (which became AN-5780-2) Wheel and Flap Position Indicator, General Electric part number 8DJ17AAK, was used in aircraft with a nose wheel (vs tail wheel aircraft). According to the US Army Air Force Interchangeability Cross Reference Chart dated February 1945, the A-3 indicator was used in bombers B-26 Marauder, A-26 Invader, and A-20 Havoc, as well as in the fighter P-38 Lightning (see image from P-38 flight manual showing location of the indicator).
The position of the wheels were indicated by the 3 small window insets, one each on the nose and each wing. The indicator in each window inset would display whether the wheels are up or down, locked or unlocked. The position of the flaps was indicated in the small window inset at the bottom, by showing increments of quarter fractions from Up to fully extended Down.
The glass and case are intact and the dial content is clear and precise. Measure 3.25 inches diameter and ~2 inches deep.