Wow - that little machine is cool - I wonder if it was a toy or what??? Looks like it would be fun to test it out.
The thing in the back of the Viking is probably a disk or what ever - it changes the stitches - there should be a cam stack or something inside it. I got one once at a GW and that part was broken inside - they aren't repairable - if it all works you have a really nice machine.