I'm not qualified to determine when anyone has mastered a martial art. But the term "Master" seems to connote a certain something. Gravitas, knowledge and talent maybe, I don't know, but definitely respect. We'd probably all agree on the respect part.
I've addressed a lot of folks by "Master". Everyone addressed them that way. Wally Jay we addressed as "Professor" but that was pretty much the same thing, at least to us. (Maybe everyone calling them Master made it so, I don't know.) But Joe Lewis, Bill Wallace and Rickson Gracie had us address them by their first names. Sometimes we'd call them Sensei out of Martial habit, and a lot of times we'd answer a question with "sir", but that was pretty much out of habit, too. But they were definitely Masters.
Ray Leonard worked out at Billy Blanks' school for several years, but everyone called him Ray. We'd address him as Champ in front of students, but that was out of respect. He was a Master, too, and in a very difficult and unforgiving art.
If you were to walk into our dojo and introduce yourself as Master, or if someone else introduced you as Master, we would address you that way. Regardless of your age or resume. It didn't much matter to us what you wanted to be called, we would always respect it.
My black belts that go on to teach get to choose what their title is. Most are Sensei, but one prefers Shihan and that's how his students address him. They (the instructors) do not have the option to have their students address them by first name. I suppose one could choose Master, but there would be too much laughing. I get to be called "Coach" because that's what I've earned and that's what I choose.
When us old guys are out and meet a young Master we usually share a wink and a nod later, and whisper to each other, "Young Master much faster!" But that's usually in harmless fun. Usually.
I've addressed a lot of folks by "Master". Everyone addressed them that way. Wally Jay we addressed as "Professor" but that was pretty much the same thing, at least to us. (Maybe everyone calling them Master made it so, I don't know.) But Joe Lewis, Bill Wallace and Rickson Gracie had us address them by their first names. Sometimes we'd call them Sensei out of Martial habit, and a lot of times we'd answer a question with "sir", but that was pretty much out of habit, too. But they were definitely Masters.
Ray Leonard worked out at Billy Blanks' school for several years, but everyone called him Ray. We'd address him as Champ in front of students, but that was out of respect. He was a Master, too, and in a very difficult and unforgiving art.
If you were to walk into our dojo and introduce yourself as Master, or if someone else introduced you as Master, we would address you that way. Regardless of your age or resume. It didn't much matter to us what you wanted to be called, we would always respect it.
My black belts that go on to teach get to choose what their title is. Most are Sensei, but one prefers Shihan and that's how his students address him. They (the instructors) do not have the option to have their students address them by first name. I suppose one could choose Master, but there would be too much laughing. I get to be called "Coach" because that's what I've earned and that's what I choose.
When us old guys are out and meet a young Master we usually share a wink and a nod later, and whisper to each other, "Young Master much faster!" But that's usually in harmless fun. Usually.
Tell your student. I have no way of knowing where anything in Asia came from a thousand years ago! I have no dog in the fight. All I know is that nowadays, when I go to the supermarket, just about everything comes from China! 
