I'm betting my DL has the post mil threads.
S99VG brought up a good point although the government wasn't messing with things like this much until 1968.
The Browning Brothers stamped Savage 1899's they sold with their address which was probably just advertising. I think I heard they stamped Winchesters also and probably all the guns they sold. This is a fun topic but I bet we never get the whole story.
They have been fighting this fight, albeit maybe not with such lack of reasoning , long before 1968.
https://www.atf.gov/rules-and-regulations/national-firearms-act
