I emailed this seller after I saw this listed in the Indian War section. IT IS A MODERN FAKE that has been floating around the gun shows for a few years now. The price is the first indicator- $20.00 with no reserve. Also, look at the edge where the "image" joins the mount. Notice that they didn't even bother to totally cover the original image with the fake one! The original image was taken by Goff at Ft. A. Lincoln, D.T., not "E.L. Brown, Sterling Illinois"!
What is also strange is that id on the verso. A very lame attempt at applying a "period ink" identification! Very obvious to me, an experienced dealer, but very tempting to a new collector. I owned the Calhoun cabinet card owned by Thomas McDougall and I sold it 7 years ago for $4000.00! Look at that description. I will watch this one closely!