Photo of a man on a horse, writing on the back is faded, but I believe it reads "JACK O. 1945."
Found in "Five Weeks in a Balloon" by Jules Verne, published by W.L. Allison Co., circa 1880s.
Ed: This is really fantastic photograph, it has a clarity and glossiness you don't see with older photos. I apologize for my skills on the digital camera, the image above really doesn't do it justice. This may be my new favorite FB.