What Joe said. Your machine looks good in the pics. You don't need anything more than oil to get it clean.
NophaDesertRat, the brown crud may have been the shellac clearcoat lifting off. The shellac gets pretty fragile with age and anything harsher than sewing machine oil can damage it. I'm not familiar with newer Goop products but IIRC the old hand cleaner had pumice in it. Avoid any abrasive cleaners as well.
Rodney