Yes, that is an Italian 4-foglio... Kirby said it was backed a while ago before Japanese paper (between the linen and the poster) was available in a single sheet that large. They used two overlapping pieces, just like the poster, but apparently it shrunk differently in that spot. It sounded like if it had been flat it wouldn't have been noticeable, but instead it was stored rolled which is the reason for the center wave. I've been dying to get some nice original paper for this film as the 1-sheet is kind of boring, but I'm not sure I'm interested in this particular copy. Great image though!