HOST: Finding an old treasure in an old building is pretty exciting, but can you imagine finding one that's as wide as a house? Poster expert Nicholas Lowry discussed one such find on our visit to the Pawnee Bill Ranch in Oklahoma.

APPRAISER: Pawnee Bill was one of the Wild West's great impresarios, second probably only to Buffalo Bill. And for years, he ran this incredible Wild West Show that entertained people not only in America, but in Europe as well.

HOST: Let's take a look at this, and to call it a poster is a stretch, I think. It's more than a poster.

APPRAISER: Right, technically it is a poster, but what we refer to it as is a barnside. This image is 70 feet long by ten feet high. And in fact, this poster survives today luckily only because a building about 60 miles away from here, when it was being refurbished, somebody built an exterior wall outside of the original wall that housed this poster, and then about 30 years ago, when they were remodeling the building again, they uncovered this poster and brought it here slat by slat, recreating it so we have this amazing image. Originally printed on paper, they were pasted up on the sides of barns. To the best of my knowledge, this is the only copy of this poster to exist.

HOST: Could you place a value on this?

APPRAISER: This poster is a great example of the motto that rarity doesn't always equal value. This piece is so big, it's virtually impossible to sell, making the poster legitimately priceless.

HOST: Well, it is a beautiful piece of art, and thank goodness the people here have done what they can to preserve it so beautifully and let the public see it. Thanks, Nico.