Rocketman, I understand your points and the usefulness of your guide. I particulary agree with this:

"Like it or not, it is necessary to consider brand name in any valuation."

Valuation is the key. Revelations sometimes happen and one of mine was a call to evaluate, along with others, the worth of an unsigned SXS, Brimingham proofed, superb craftsmanship.

Everyone looked intently for a name, or hint of one. No one considered the plainly visible quality features. Objectively it was a superb SXS boxlock ejector which the learned company seemed to agree would have to be valued at under an AYA No 4 due to lack of a name. That was the day I learned a lot about shotguns and lots more about people.