Robert Lansdale: As soon as I saw that big lens on the back I thought of a Solar enlarger as patented by D.A. Woodward (improved patent
Patent No.151,462 of May 26, 1874 showing improved construction of solar enlarger and mirror assembly) This instrument would be installed as part of a portal in a darkroom window where, outside, a moveable mirror would gather in the light, project it through the big lens, then thorough a negative and then through the process lens. The enlarged image would be projected to sensitive photo paper on a moveable "wall". First patent: U.S. Patent No.16,700 dated Feb. 24, 1857. We (PHSC) had a full story of the Woodard enlarger by Matt Isenburg in Photographic Canadiana Vol 37-4 Feb-April 2012. PDF available.
As part of the detective work you might find burn marks on the inside of the camera where the operator failed to move the mirror and the image of the sun shone on the inside bellows or wooden parts and burned it.