It doesnt matter at all. Just need a lens shutter combo unit like whats on an agfa isollette or similar. I have one that works so i an not going to tear it part.
I just got a shutter/lens combo of an Ansco B2 Speedex Jr, apparently 6x6 coverage with the retaining ring. Rick A included it in a box of free stuff, I could pass it on to you.
Shutter seems inop but I'm not sure. Has stops from f/11 to f/22 but would open at least another stop if you figured out how to get the aperture blades out of the way.