Unfortunately, no known copies of this film exist. Hitchcock claimed it was as it should be, because it was a "very bad movie". But others have accounted that it was as good, or better, than The Lodger. I remain hopeful that a copy of this film is found someday so we can judge for ourselves. Until a few years ago, it was believed that all that existed were 6 still images from The Mountain Eagle. J. Lary Kuhns found a complete set of stills in Hitchcock's private collection. From looking at the photographs and reading about the film, it seems like one that I'd like to see. I imagine the last still photo of the guy laughing to be the end of the movie and his response to some final twist.
Hitchcock's Notebooks by Dan Auiler (1999) has, by far, the most information about The Mountain Eagle, including: a detailed trade review of the movie that was in the Oct 1926 Kinematograph, an excellent account on the making of the film by Hitch, as well as most of the still pictures associated with the film (see below).