The most widely used of the WW II military
straight keys. Had black oval plastic base inscribed
"J-37" and either brass or nickel plated
screws. The levers were made of nickel plated or black
anodized steel. There was a leaf spring used in J-37
to return key lever.
key was a principal part of several US Signal Corps
keys like J-44, J-45 or J-47.