Kittywolf, what you see under that metal plate in your pic is the knee controller. It looks different than the one that I have, it looks like it -might- be missing parts, but your dad might be able to rig it. It might also just be incorrectly assembled. Meaning, there's a chance that knee lever could work, it could be a convertible.
The only "cable" you'd need to make her work, assuming the wiring is in good shape, is a regular single lead cord. Similar to tucci's, just not with a pedal attached, that's taken care of by the knee lever. If you can post a clearer pic of the inside of that box, where the controller is, I might be able to figure out what's there and what's not. I'll try to post a pic of mine tomorrow too, so you can compare.
I have boxes here that started out looking as bad as yours. In most cases, I wiped them down with a damp cloth, or in extreme situations, with murphys oil soap, and then applied Howards "Feed'n'Wax" -
http://www.homehardware.ca/en/rec/in...kgu/R-I4548388
Oh I just had to post that link! It's canadian, and at a hardware store, instead of just at the antique stores where I usually find it.
That work though is after a little love with some clamps (I think the ones we have are "Irwin") and either wood glue (regular old elmer's etc) or Hide glue (it might be the Titebond brand that PCDH mentions). I have some here, so I use it. It's a modern version of the animal glues they used to make the cases in the first place.