Sooo... my definition of 'best gun' is the best effort of a top tier maker.
Beg pardon, but I have to disagree with you on this point. The "trick" was not being able to make a best work gun. Rather, it was the ability to get a commission to do so. Retailers, as well as trade masters, all knew who to approach within the trade for best work and how to get a best gun to their specifications and with their names. Brand Value (what a maker's name adds to a gun's value) is much more due to the maker's ability to attract commissions for high Original Quality grade guns. The ability to attract commissions is highly tied to name recognition the shop was able to grow and which social circles of London dealt with which dealer(s). Social circle members tended to trade with select tradesmen for craft goods. Buying from a shop that generally traded with a higher circle was risky business. It might be construed as social climbing and, unless you had the money or extraordinary skill to back it up, that was risky indeed.