There were numerous variations. The C was a P rear with an F1 front standard, not the later f2. But that's the nice thing about the system - the sheer interchangeability of components. But every now and then, someone cobbles together spare parts and tries to deceptively sell it as such and such a model it really isn't. But converting a 4X5 F2 to anything 5x7, buying separate needed components, might cost you considerably more than buying a 5x7 camera outright.