I found some info on magic erasers here:
https://www.yourmechanic.com/article...r-by-kevin-woo
Quote: "
Magic Erasers are made from melamine foam. When a Magic Eraser gets wet, its abrasiveness is the equivalent of 3000 to 5000 grit sandpaper, depending on how hard you scrub. That might not sound very rough, but on car paint the damage could be severe. Worse, if you have a heavy hand and go to town with a bone dry Magic Eraser, it would be similar to using 800 grit sandpaper. In either case, using a Magic Eraser to clean a spot on your car (or in this case, sewing machine) will scratch the paint."Here's more on melamine foam from Wikipedia: https://en.wikipedia.org/wiki/Melamine_foam
I don't have a clue what those spots are on that machine. Is it also on the other side, do you know? Since the back would be the "up" side if the machine was in a cabinet, the discoloration could have come from exposure to something while in the cabinet if it's just on one side. Is it a cast iron or aluminum machine? If there is an inconspicuous place, you could carefully try a tiny spot of rust remover like Must for Rust and see how it affects the paint. Or have you tried the old cleaning standby: sewing machine oil?
Andy Tube channel on YouTube has some good advice on using automobile cleaners and waxes on sewing machines.
It's a nice machine, hope you can make it look all nice and gleaming again!
MJ