Not the '40s, but I looked at stock in the late 70s early 80s with my old AE-1 Program. You had to shoot slide, print multiple copies, label them with what little info could be written on the edges, mount them in plastic sleeves and fed-ex them around the country. That's after shooting and processing.
Maybe not much has changed, but what gets done in a few minutes now took many hours back then, plus the expense of producing stock submissions.