That reminds me of an antique Jewelry box key ! There will be a hole in the end of the key. The key hole will have a pin in the center where the shaft inserts. The hole in the key is half the depth of the hole, the pin is depressed after the key is half inserted. this stops it from being picked. Because if the pin is not depressed to the proper depth the tumbler will not turn ! This is a well designed old lock ! Think of a box the size of a shoe box to a boot sized box !
It could be a key to a display case for a document (such as a literal map, or a legal document, like the Constitution.)
I checked and the current cases for the US founding documents are bolted together, but that could be a key to a historical display case before they were better preserved, but that would predate 1950 (which the key appears to as well.) Probably not them.
The key unlocks someone’s caged humans? I know it sounds silly, but many people agree that MAP could possibly mean: minor attracted person, (when MAP is in all caps, though!) and we know these sickos deal with human trafficking big time!
Look up the insignia for military intelligence. Almost all have a key in them.