Could it have been an 11x14? I know that there are several fine 11x14 cameras almost identical to this one out there. I believe that George Eastman may have bought the company early in the history of EK. At least, I have seen one 11x14 about identical to yours but with an Eastman Kodak plate on the front.
Entirely likely. I haven't measured the back exactly, pending getting it apart without damage; but it might well be an 11x14.