Koss Corporation in Milwaukee Wisconsin began making headphones in 1958.
These model Pro/4AA headphones in a green/tan and black color were made by Koss in the 1970s in the United States.
I didn't have equipment to test them but someone tested them for me with their stereo equipment and they work.
They are in vintage condition and would add a touch of 1970s music retro to a collection.
Ships USPS.