These cameras came with backs that had a matching serial number as shown on the right.  In addition, a pair of brass rollers and ebony film plate should be present minimally.  If lucky, it will also have the optional circular, square or oval frame insert and original box.  In the past decade I have only seen one example with the interchangeable back and light-tight cover offered for sale.  Most have the oxidized silver finish worn or even (horror) polished off by some misguided though well-meaning attempt at restoration.

Resource:  The Kombi is an especially interesting and important camera that introduced several notable innovations.   Scott's Photographica Collection includes a rather comprehensive description of the camera and the Kemper company and it has been a valuable source of information.  I sincerely encourage anyone who may be interested in this camera and its history to visit the website.