Depends, it's usually stamped somewhere on the receiver unless it was a early import. I've seen them with no markings except for the importer, like with early pre-89 B-west imports. Factory markings may help, but they are covered in the pic. I have seen them with no factory marking save for a serial number, again this was on a B-west pre-89 import. Also Norinco and Polytech where often made in the same factory. It just depended on which company sold the rifle to the importer; the civilian one or the government/military one (I can't remember which is which).
Only thing I can say is it's a pre-ban stamped Chinese AK made in China and imported (not assembled in US on a US receiver). It's got some wear but I think $650 is a good price no matter what, I would buy it. If it's not marked with the Norinco symbol or "norinco" or "poly technology", and that would be on the receiver it's self, it's an early pre-89 and doesn't not have to comply with 922r (needing US parts). It's not a converted MAK-90 and isn't Polytech Legend (milled receiver).
ETA: on the LNIB B-west I could have bought the only markings were: MADE IN CHINA B-WEST *whatever city and state they were in* AKS-47 with the serial number on the trunion but no factory code. That's it. It was a stamped receiver with an under-folding spiker. Could have gotten it for $750 and kick myself every time I think of it.