All this causes one to wonder who should really be described as the manufacturer. Especially for purposes of filling out the federal forms, registration, etc.

Are we assuming that W&S engraved the "William Evans (From Purdey's)" on it? That would have to be done before blueing. I will have to go back and look at the style and quality of engraving for that phrase as opposed to the chambering engraving.

Wm. Evans #9237 W&S #11906 (It's upside down, I almost read it as 90611)

As an aside, I once saw a Wm. Evans single shot chambered for the 400-360 Purdey that had far and away the most fabulous case hardening finish on the action that I've ever seen. (Memory's a bit slack, I don't recall if it was the original finish.) It was incredible, not to be believed even looking at it and an order of magnitude better than the best of any other case coloring I've ever seen.