I recently saw an exhibit at The University of Florida from a private collection - there were lots of images I had never seen before, either as prints or as reproductions. There were a number of small prints from the late 20s and early 30s. Some that I believe to have been contact prints were 5x7 - others were 4x5. There were also a few prints at slightly smaller than 5x7 that, according to some of the books, were originally shot with a 4x5. So he must have enlarged some prints only a little bit.
juan