Could also have been a “walk across” from Canada. Before the 1990s the border was once almost wide-open, and lots of firearms (both legal here, and not so much) came through in American vehicles.
Also, back in the day, State Department, Foreign Service, and other government personnel returning from overseas were not subjected to a detailed search of their belongings, and some who had bought weapons for personal protection in their foreign posts (not necessarily legal here) brought them back into the US.
As an example, both of the above situations have been cited as means by which “G series” FN-FALs not on the “ATF amnesty approved” list (a story in its own right) have appeared over here.
It could be a canadian walk across. On clear days I can see Canada from the end of my street.
CC
I was in a local gun store when a guy walked in with one of those FN’s. He had inherited it from his Uncle and had no idea what it was. Story ended badly. The guy next to him at the counter was the local ATF book checker, he called the enforcement guys and off the gun went to their private collect - or so I am told - along with threats of prosecution. God I hate the ATF.