Primo Jr. Damn! I just couldn't think of the name.
The condensors on some projectors (not Sawyers...LOL) might be a bit tight for fully illuminating the corners.
Durst made an enlarger, the 404, for the format. These days it might be difficult to find 4X 4 negative carriers for any enlarger. >>
Well, we might have missed that, projecting on the wall. ;-)
I may have been contact printing in those days, I think I have a folder that takes 8 exposures, decent size format at that.
I heard the UK was making this and 620 film for a few years longer than the US. Some of my students used my mom's instamatic to shoot Kodachrome on a western US field trip, the slide projected quite well and square works quite well in presentation. I have a few boxes of mounts, just in case I shoot some.
I think my first enlarger had one carrier, with two sheets of glass, a Federal and I cannot believe I actually was able to sell it years later when I got an Omega. ;-)
John