If there are no markings on the outside of the camera, (did you check _under_ the handle on the top of the camera? Sometimes the model markings are pressed into the leatherette there), try colapsing the lens board back into the camera and rolling the rack out without the lens. Sometimes markings are hidden under there. If there are no markings, your guess is a good as mine! ^_^
I checked all kind of places but i didn't found anything. I'll stay with what i found on Camerapedia (japanese First plate Folder made in ~1930?).