The office responsible for the relics is the Tank and Automotive Command, Warren Michigan and its the Donations Department. There is a relativle new woman working there who replaced Marilyn about two years ago. They are getting real sticky about this stuff too. We ran into a situation where we restored a 3 inch howitzer for the state veterans home, and those folks found out about it. Years ago, right after the war and BEFORE BATF, you could legally buy those pieces from the govt. The owner of one donated it o the home, it was pretty ratty so we did the work as a public service project. The , (the home) got a Sherman donated to them for display and were getting an M-60 as well. The folks in Warren needed the pictures of the site, and in the pictures were the 3 inch gun. It wasn't on their list as a relic with the home and when they heard the story, they asked to see the papers. There were none. So guess what, it IS there gun now, donation from someone else or not. They threatened to go to court to secure it.
Its a real problem, there are legally owned private units out there, but without papers, because of the BATF, the TACOM is cooperating in getting them rounded up from private owners.