Just measure the ground glass. If it's 4x5, it's a 4x5 camera. If it's 3.25x4.25, it's a 3.25x4.25 camera. I wouldn't think those holders would fit a 4x5 back though. So if the holders fit, you have a 3.25x4.25 camera, aka quarter plate. Film will be cut by Ilford as part of their order. Freestyle still has Efke 100 in stock but of course that's going away. It's a hard film to find.