Compass, 2 Gou, Japanese Army Aircraft, Tokyo Aero Indicator Co.
This is a WWII-era direct reading magnetic compass,Type 2 Gou, made by Tokyo Aero Indicator Co. The Type 2 Gou was primarily used in early aircraft of the Japanese Army such as the Type 99 Kawanishi Ki-48 Lily Light Bomber and Type 97 Mitsubishi Ki-21 Sally Bomber, according to the online Funatsu Aviation Instruments Museum.
From our examination, it appears that the compass would be affixed to a pedestal or a mount where it could be viewed from directly overhead for accurate reading. There are 3 uprights which hold the compass body to the base and suspended on 6 vibration mounts. The upright with the white vertical marking opposite the data label is positioned forward, or toward the nose of the aircraft. There are markings on the base at the front and read to precisely mount the compass. Looking downward, the degree markings internally would show zero toward the nose of the aircraft. The larger end of the compass needle points north. The difference between zero and the north-indicating pointer is the aircraft's direction of travel with respect to magnetic north.
At the top of the compass is a rotatable glass lens with parallel line markings and degree markings around its perimeter. By rotating this lens to align North with the compass pointer below, the pilot or navigator can determine when the aircraft is correctly on the desired course heading. The purpose of the two small upright brackets located at East and West is unknown. Compensating directional adjustment screws are located directly beneath the body of the compass.
This specimen no longer contains the compass dampening fluid, and the top glass lens is damaged. The pointer does rotate Measures ~5.25 inches diameter and ~4.25 inches tall.