Thank you everyone for your contributions. What has really helped me so far was finding this page: and this page:

The cameras pictured are almost spot-on to the one belonging to Phyllis. I wonder if what I thought was a "No. 7" was just a stylized 1. I'll have to look again.

The shutter is jammed on the camera. I might have to send it off to SK Grimes to see about getting it running again.