" So then I assume the RDIAS are ok to keep then. "
If someone had the stamp to go w/ it, yes.
I'm surprised there was a guy 'legitimately' selling them. I remember the ad in Shotgun News that ran for decades and always figured it was ATF 'selling' them. If I remember the ad correctly, payment was via COD only. I figured that was so they had the buyer actually handing over the money for the item (makes it hard to say 'hell, I didn't order this'). God help us when they figure out a shotgun and precision rifle are more efficient tools than a full-auto salt rifle.