Yuk! I'm curious about this too, as we're just noticing some nasty black spots blooming on part of our belly band.
Your post makes me wonder about the orange cleaner from the Dollar store. No kidding... it's very good stuff. I've used it for my other hobby/passion, restoring vintage sewing machines... and it does NOT harm the finish of the metal machines (NOT the black antique ones with decals... don't ever use a "cleaner" on those finishes
), but takes all kinds of gook and grease and dirt and nastiness off very nicely. Leaving a nice shine.
The mid-century machines have a finish just like auto paint
, and it can be damaged by the wrong stuff. Many of them have (yuk) decades of *nicotine* caked all over them and it's very hard to remove. This cleaner just melts the nicotine away.
I'm going to try it on the belly band tomorrow... will report back. In the meantime, does anyone know why this fungus stuff turns up, and returns?