I know he got his certificate of Hanshi (?) meaning he had the right to teach, from Itosu.If my memory serves me right...
From what I understand, Funakoshi was awarded his black belt from either the Emperor of Japan or the Emperor's family member. He was a 5th dan, which was the highest dan rank at the time. He was awarded 10th dan by his students after his death. I don't think Funakoshi ranked anyone any specific dan rank, just ranked them as black belts. If he did give actual dan ranks, they most likely weren't higher than 3rd or 4th. One of his senior-most students wouldn't accept anything over 5th dan because he kept with the 5th dan as the highest rank tradition. That was several years ago, so he may have passed away since then and possibly been promoted posthumously. I know there was a strong contingent who wanted to award him a 10th dan. I can't remember his name to look it up.
You raise some good questions. I'm not a historian, so take what I say as you will...I know he got his certificate of Hanshi (?) meaning he had the right to teach, from Itosu.
There had to be a Dan system by the 1940's because Im always seeing ppl saying that they were promoted by Funakoshi to "this level".
Im just curious to how long did they train before they were handed their Dan certificates?