Hi Pete,
I don't know much about it. It was in such a bad shape that I took it to my repair guy on the same day. I noticed that the big spool you see there (there are actually two of them) goes on the side of the machine, just like its big sisters. I guess he's just moved it to the position you see in the photo to make it easier to adjust things.
The colour selector is not functional, I think.
As for finding ribbons for this particular machine, just forget about it. Apparently, I could use the ribbons inside the Olivetti Praxis' cassettes, which are still available.