I can offer a bit of insight into the packaging of the Norweb coins. I bought some of the Ancient British material in Spinks' sale number 45 on 13 June 1985. These coins were (obviously) not slabbed, so we can say that not all the Norweb material was slabbed.

The coins I received came with the original Norweb 2X2s. These have a distinctive spider web motif printed on the flap. It would be a simple matter to identify the provenance if the coins managed to stay with their envelopes.

I believe I can shed some light on the question raised of how NGC was able to attribute a Canadian coin to the Norweb Collection. NGC will add a provenance to a coin if it is submitted in the sealed flip from that sale or may be plate matched with the original auction catalog. In rare instances we have done this for coins attributed to a particular collection in a subsequent auction, as long as we have faith in that company's cataloger.

It usually falls to me to do this for American pieces, while our world grading room attributes any coins or tokens made outside of what is now the USA.