spring tour 1975 poster

[DavidMn]

I think most people have heard of this poster. I paid alot of money for it, $300 to be precise, but there's no writing on the bottom, and no wrinkles on it, except for a couple in a 2 corners. The guy I bought it from told me that not many exist that arent written on and are in as good condition as mine is. I need an experts opinion on this. Is this true what he said about how rare it is? I'm not an big time expert on the subject of this, but it definitelly looks like an original