Cool find!
It looks like the right paper. The condition isn't very good with the tobacco staining but these things are pretty rare. Two things set off little questions in my mind - the border at the bottom seems extra long and the type on the left bottom curved down slightly on the originals I've seen. Your pictures are pretty small and I'm only knowledgeable because I've seen several at auction, I'm not an expert. Compare your poster to this known original in the Wyoming State University collection.
My gut instinct says you probably have the real thing. If so I'd guess with the current condition at a good auction house on the right day you might get $6,000 - $10,000?
If it was mine I'd run it by Jemison Beshear, he used to work with Greg Martin and with Bonhams and Butterfields in the San Francisco house. He really knows this stuff better than you or I and he's got the connections to find a buyer for you.
