this is certainly a comment from the "peanut gallery", but i would question the third possibility offered by Argo. i suspect that in this case, the second possibility is much more likely. my reasoning is that the wr patent includes both the action & barrel set....not at all the same thing as fitting a purdey bolted set using no third bite.

"it's a poor sort of memory that only works backwards."
lewis carroll, Alice in Wonderland