Welcome to the forum but unfortunately that helmet isn't even close to the ESB design and certainly not screen used. Like Noisetrigger said, hope you didn't pay a lot of money for it.
All that being said, as long as you enjoy owning it, that's all that matters!!
Sorry man. Does the seller take returns?
Also, how many helmets did they make for the production of the movie? I can't see them making 15, that seems way high. I'd think maybe 6, but definitely less than 10.