The term "Master Craftsman" has a very specific meaning. This term is left over from the European system of guilds and has a modern implication as to who is qualified to work in certain fields in Europe. It's like the word "doctor" which is both a description of someones work and a distinctive title applied to someone who has completed advanced training.
I don't self apply the term "Master Craftsman", even though I believe that the quality of my work is exceptional. In order to be a true Master Craftsman, it takes many years of schooling and a very rigorous exam. Passing that test and receiving a Meisterbrief is a huge accomplishment and I believe in showing the appropriate respect to those that do it by not taking a title that I've not earned.
Take my teacher Rick Seraphinoff and our friend Michael Munkwitz as an example. Together, they host a trumpet making workshop every year. Michael is a certified Master Craftsman but Rick is not although both are heavyweights when it comes to making period instruments. I have never heard Rick refer to himself as a Master Craftsman, despite his incredible skill. Stories Michael tells of his examination make it clear that it is a very special and remarkable achievement. The process and those that have completed it deserve a great deal of respect.
Rick did give me an exam and made me complete a work at the end of my three years of training (the very first version of my single Bb/ C ascending horn). He even gave me a "Meisterbreif" which I cherish very much. But while his attempts to give me a complete experience were very meaningful to me personally, they don't have any value outside of my own experience.
Make no mistake, if there were a procedure to earn a Master Craftman's title here in the US, I would be there. I know that Rick and many other American craftsmen and women would as well. We simply don't have a tradition of that here in the US and we all have to find other ways to distinguish ourselves. I try to do it with my work and leave the titles alone.