This instrument measured the turn angle of the aircraft.  It was connected to the air pressure system  and works on a vacume system and was located on the main instrument panel. Made of aluminum, this horizon dates around 1943 and would have been used throughout the war.  98% of the original finish remains, and there are no dents or damage!  It is still factory sealed, and the data label is 100% intact.  The dial still glows when UV light is applied.  Pictures speak for themselves, a near mint example