I'm a (non-expert) skeptic fascinated by this. My skepticism, personally would be met by two elements a) A message identifying himself signed with a key from o

I'm a (non-expert) skeptic fascinated by this. My skepticism, personally would be met by two elements a) A message identifying himself signed with a key from one of the original blocks. b) Testimony of one of the early BTC people who interacted with him that he is the same person. a alone would mean he could have otherwise acquired the keys, b makes this unlikely. b has been provided, but it is insufficient without a.