Polish AK receiver blank

[Viking350]

Got this in an email from Wideners. Figured I would post it here for all to see. I know nothing about building AK's just thought it was interesting since these have no serial numbers on them.

http://www.wideners.com/itemdetail.cfm?item_id=100000564

[Tom]

Cope's sold out all they had. Nice receivers! Bought two from them. Thought of getting some more, but bought a flat from AKBuilder to use as a reference since the Polish blanks don't have holes drilled. The flat from Curtis is sweet!
Gonna use one Polish blank for the Polish kit I have, not sure what the other will be used on yet. Thinking of re-building my other AK's with the new flats from Curtis!

[Tx Dogblaster]

Those look nice and the price is right!!! My only concern would be the heat treating. The ad doesn't mention anything about it. As long as they're 4130 or 4140 annealed then spot treating the axis holes isn't a big deal.

[Viking350]

Since there is no serial number on them, do you have to file any paperwork when you complete the build?