Back in the 1970's, the local portrait/studio photographer would come to our high school each fall to do the student pictures. I don't know the specific kind of camera he used, but I do know that he used 5 x 7 film and a shifting back similar to that shown in Photographica's last post. We had an enrollment of around 500-550 students at the time, so he would have needed a couple of dozen sheets (assuming 24 shots per sheet) for the whole job. He probably used hangers in dip and dunk tanks for the processing (maybe a dozen at a time) so the method he used is actually a rather efficient way to do the job. I just don't know how he had the concentration to avoid blanks and double-exposures!