I have a late 1961 or early 1962 Nikon F with the standard prism finder. As I recall on the earliest F models, a factory retrofit modification had to be made to the screen box before one of the later Photomic finders could be mounted on the camera. What year model or serial number designation was the cutoff where no modification needed to be made to fit the Photomic finder? And once new model manufacture no longer required a modification, were all subsequent Photomic finders compatible? Thank you.