Tucson Police Department has a Thompson submachine gun on public display in the lobby of the police hq. Don't know if it's registered or not, but that is irrelevant as it will never be sold. It was seized from a Dillinger gang member when they were captured here in 1934. On rare occasions, it is removed from the permanent display and shown at local Dillinger Days events.
Years ago, it was displayed at a Dillinger Day event at the old Fox Theater in Tucson. After the event, while the officer in charge was waiting for the police transport that was to take the rifle back to the police department, the officer allowed the gun enthusiasts to hold the gun to get their pictures taken with it.