I know two of the people you are referring too and can guess on a couple of others.

In one case I knew the seller was lying about the rifle and made an offer that reflected it.

The offer was accepted.

I once saw a 577 BPE being represented as a Nitro rifle. It even had a 'proof' that said so. The 'proof' just said
CARDITE APPROVED.

I think The guy now does lettering for Searcy.

The guy that used to own Cape Outfitters used to send BP rifles to Belgium. There the Flats were polished off and new Nitro Proofs were added by a local gunsmith. The rifles were then shipped back for sale.