You know I could tell you from experience from watching my dad. He says "I teach hapkido" he doesn't say I am a master, have mastered it, whatever. He doesn't even like to wear the dobok with the 5th dan trim. He will call himself Mr. Morton, on several occassions I have heard people call him Master Morton, he said "Nope, I am not a master: x,y, z are but not me.
I workout under a GM and a Master in TKD that also hold master rank in hapkido the same as my dad. Also a 4th dan tkd and hkd. You know if you call these nice gentlemen sir they are happy.
I know by KKW you can be called master at 4th dan. I told our 4th dan this, he is a certified tkd sparring and ring person. Anyway he said he could be called master at one of two times. Promotion to 5th dan, or when he is as good at tkd as GM Hildebrand.
Just to throw in one more example of humble.....on Sunday dec. 10 Derekhkd and a few others tested and passed their 3rd gup tests. We all went out to eat. Well we have a tradition that the lowest ranking belt goes to pay the bill after the money had been collected etc.
I went and paid it, even though I have a dan rank in judo...I had not tested for my 5th gup in hapkido nor my 4th gup in tkd. I figured the whole tabling area was filled with 2nd dans and above with the execption of the 3 who tested and me. So I said, my dan rank is in another school and art. I don't care, everyone finish eating and went and paid.