They definitely exist, I last used one in the period 1970 - 1972 when I was working for the V&A Museum in London. I now have a De Vere 4x5" Universal Camera, hexagonal rail and all. I believe the 8x10" was made chiefly as the later "Devon" model with a square rail (apart from some early copy cameras which were thinly disguised enlargers). They are good solid cameras, on the heavy side, lens panels almost impossible to obtain but not too bad to make (2 mm thick, 140 x 140 mm, totally flat with no light-trapping). Probably worth buying in the present market only if in excellent order and cheap!