Why would shirts sold in the US have size marked "TG"? for extra large?
Stuff is sold to distributors, and they sell to the highest bidder. Military stuff is supposed to have an end user certificate, that flows back to the manufacturer, and assures that all is on the up an up. Of course if that is forged, or if a part legal on one application is cannibalized onto another, the regulatory system breaks down.
In theory, a serial number can be traced from the manufacturer to the distributor, and thence to the end user. Then you can find who cheated, and they can be fined or jailed.
If it is traced to a company that doesn't exist any more, then you have no recourse.
I have a demilled and non-functional AKM that I use as a training aid. It was never intended for sale in the US, yet it's marked in Cyrillic and English.
I also have a Saiga shotgun, which was intended for sale outside Russia. One rollmark says "Made in Russia" in Cyrillic, and again in English - all as part of the same marking.
English is the universal commerce language. Even the MAS series of rifles is stamped in English as well as French.