Although the camera may be considered uncommon at best, it has been a favorite of collectors for the past century. It isn't a true investment since prices have remained fairly constant over the last decade hovering about $150-200. However, with the original box, and in particular with the optional interchangeable backs complete with covers, prepare to pay up to $500 or more.
The original design for the Kombi was the product of William V. Esmond to whom the patent was issued on December 20, 1892. He had assigned half of the rights to Alfred C. Kemper. Presumably, Esmond was a business associate of Kemper who was provided the rights to commercialize the design. As can be seen from the original patent, details of the preferred embodiment represented in the drawings differed substantially from that which was actually manufactured by Kemper. Apparently, there were no patents issued specifically covering the interchangeable light-tight backs.
The Kombi was exceptionally popular throughout the decade of the 1890's and into the beginning of the 20th century. It was produced and sold by Alfred C. Kemper of Chicago, Illinois.
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.