I believe Greener’s top of the line best gun, at the turn of the last century, was the self acting ejector, a box lock gun. He did produce side lock guns at the same time, and they cost less than that model.
My opinion only, but, the part of building a best that is often missed is the effort put into keeping the design serviceable by even a partially skilled gunsmith. I look at the Holland Royals as being better in that regard then the Beesley patent Purdey’s. But, it is almost never brought up.

Best,
Ted