Give a four year old a box of crayola crayons and they can do a better job.
Signed by the 2'10" Stan Lee from the Beijing Circus. That's the smallest Stan Lee signature I've ever seen, and we're talking about thousands of them.
You can go to WaltDisneyStudios.com and search for Kevin Feige (who is the President of Productions at Marvel Studios) There, you can Contact him and ask if these Posters exist or if that's his Signature on the COA. This way, your Guaranteed an Honest answer on the Poster. I think he's on Twitter too.(KevinFeige@KevFeige)......Good Luck.
There you go. Pete just answered the question and the Signature on the COA is Fake, so I'm sure the Poster is as well.