Very interesting piece of history.

Untested, missing parts, but very, very cool!

Sold as-Is. For parts or repair.

Marked ID-6 A/APN

According to what I could find out, this was the first Loran set for aircraft to enter service. 

Indicator unit Type ID-6-A/APN-4 from Loran navigation aid, and operator's viewing hood, used by American US Army Signal Corps. LORAN (LOng RAnge Navigation) was a hyperbolic radio navigation system developed in the United States during World War II (1939-1945).

LORAN was an American development of the British GEE radio navigation system (used during World War II). While GEE had a range of about 400 miles (644 km), early LORAN systems had a range of 1,200 miles (1,930 km). The APN-4 unit was developed by R J Dippy, the British inventor of GEE. He was sent to the USA in mid-1942 to work with the LORAN development team. It was Dippy who ensured that the LORAN unit was interchangeable with the in-service GEE unit, so could be fitted to all RAF / RN aircraft.. LORAN was used in all theatres but was especially valuable as a navigational aid in the Pacific where aircraft had to traverse vast stretches of open sea with no landmarks from which to take bearings.