Something is weird. He provided a message and a signature, but there's nothing in the message to indicate that he signed it himself, or when it was signed. It could have been signed months or years ago and there's no way to prove otherwise.

He needs to sign a message provided to him right now - or otherwise show ownership of coins in early blocks by moving them around.

Edit: He apparently haven't even provided a valid message/sig, so the whole thing stinks.