The 15-91 works which is the main point, but it has a film of grunge. The film is only in parts. The photo shows it clearly. The top is clean but the lower part isn't. The flash made the grime layer show up more than it actually does. The problem is cleaning it without damaging the decals or scratching the paint. Everyone has their favorite cleaner and it's a matter of testing carefully. I spent a couple of hours scrubbing and managed to get only two inches nicely cleaned.
I thought getting the machine in working order would be the hard part. Apparently just cleaning the thing will take much more time.