This the pic of the flag they sent. At the link there's a copy of it that I enhanced. Sorry I can't tell if there's a MacArthur signature in the center. Maybe you could take a close-up of the MacArthur signature itself?
I'd be interested in any press photos or news articles that mention MacArthur signing a Japanese flag in Tokyo that day. Maybe he did, but it just seems a bit out of character and out of the spirit of his new diplomatic role. At that point the military victory was behind him and I would have thought his publicly signing a Japanese flag to be a bit awkward.
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