Anyone can call himself anything he wants. Perhaps the concept of peer review needs to be considered. When recognized gunbuilders get together for a jaw session and they tend to agree that a person is a master gunsmith, he probably is. I'm not here to play semantic games and define words like "best," but we all tend to concur on who the really good ones are. And the practicing gunsmiths around here who make a living from it furthermore tend to agree on definitions of terms and criteria for determination of "mastery' of the craft.
Also one needs to ask what aspects of building a gunsmith has mastered. One may be a master at hand craft and execution, but not at the interpretation or understanding of the historical evolution of the architecture and regional characteristics of early guns. To some, the latter doesn't matter. To many others, it is a fundamental base-line necessity for any further consideration of a piece.
Also, is one aiming to be viewed as the fanciest "high-art" builder of the era or does he see himself as a production builder of working guns that are intended to be used? Some builders and apparently some customers are not satisfied unless every square inch of a gun is covered with gingerbread. Look at the early originals. The vast preponderance were not all dolled up with doo-dads. Plain guns, too, can be done with crispness and integrity or with sloppy work. Good work is good work, bad is bad, regardless of how glittery it is.
I have always refrained from using the term "master" in association with my own work, preferring the term "journeyman" instead. This I can substantiate with professional awards, etc. Compared to the best, I am far from a master. My satisfaction comes from seeing my products used in the forests and fields and I find it fun to build guns. JWH