At first, I thought maybe you were trying to help mt gox victims in some way, but this seems very suspicious. Please don't tell me you are trying to scam people into giving you 600 btc for an account that you clearly do NOT own. Also, what makes you think people with those kind of screenshots would not want to take legal action themselves? Stupidest attempted scam I've seen in a while.
It's more likely he's trying to fool the taxman, by proving that his undocumented wealth relates to him being early bitcoin adopter. Just my guess though.
Mt Gox required passport verification, screenshots only are not a proof of anything. You could probably find few of such just by googling.