Foriegn Gun, No Import Markings?

[Gunnerdad80]

What are all the ways foriegn guns can enter the USA without having any import markings what so ever? I'm curious because I've seen guns here and there without import markings ANYWHERE on them, being sold legally, that definitely did not originate in the USA.

[87CZ75]

Foreign firearms imported prior to the 1968 gun control act did not need import marks, if I have my laws right, and also firearms personally brought in by GI's as personal property did not have to be import marked in the past either, though I do not know the specifics of how that works, either then or now.  I do have a Pre-B from 1987 that was purchased by a US GI from a rod & gun club in Germany and brought back as personal property, and it does not have an import mark anywhere on it.

[double-d]

though I do not know the specifics of how that works

Then,
All imported firearms GI's purchased as personal property could only be imported with BATF approval. 
Approval came from submitted form OMB1512-0018 (Application and Permit for Importation of Firearms, Ammunition and Implements of War For Use by Members of the United States Armed Forces) stamped with an approval permit number.
Every firearm I purchased abroad required this form be submitted well in advance of importation and the BATF has serial numbers registered on each.

Wasn't easy to import my CZ-75's (plural) back in '86-'87, was rejected three times before they were finally accepted. Must have been a Warsaw Nation thing...my other firearms were approved on first submittal.
That was my experience.

[Gunnerdad80]

I have a 1990 Tanfoglio Giuseppe “The Ultra”-“IPSC APPROVED” 41AE/9mm that was not imported by FIE, EXCAM or any of the importers of the day. There aren’t ANY other markings on the gun except what Tanfoglio Giuseppe rolled on from the factory. My guess would’ve been US military or government official purchased and brought it back but I don’t know that for sure. I didn’t think about it at the time of purchase but now I kind of feel like it might actually be worth more because it doesn’t have any primary or secondary import marks on it. Is that just my wishful thinking?