I wondered about that. So they changed their policy right after that. Now there’s no proof that Tsunamigeno looked in the book. And the fact is, he didn’t look in the book they have displayed now. He was shown a different book.
I wonder when was the first point at which they said a person would have to sign in to see an index book.
I’ll go out on a limb here and say it was the next person who looked at it after TG. Bout damn guarantee it. TG did have to fill out little request slips, did have to hand over his ID, but said there was no “sign in book”.