Seems like a still version of the Bell and Howell Filmo and Eyemo movie cameras. They had a little focusing window that gave you a view of the center portion of the image through the taking lens. Then you'd do your framing through a side-mounted parallax viewfinder. Time-consuming and tedious to focus with, especially if you're trying to shoot footage of an ongoing war, as the users of those cameras were. With the Filmo you had to rotate the lens out of the taking position to pull focus, then back into place to shoot. As far as I can tell, the only reason they persisted into the 1950s was the US military, which couldn't be seen to buy German made reflex (ie, Arriflex) cameras.