Resurrecting this old thread to contribute! I tried out a Magic Eraser Sponge on my 70s Adler Tippa yesterday and my advice is to be careful because its 'magic' is actually that it is minutely abrasive.

It worked a treat to remove ink stains from the plastic body of my Tippa, but unfortunately I wasn't being careful enough and I ran the sponge over the painted ribbon indicator squares. It half erased them too! It's not a huge deal because the machine was dirt cheap and is far from cosmetically perfect, but I felt a bit dumb anyway. 

I also tried it on a non-visible patch of glossy enamel on a machine with a metal body and saw that it reduces gloss and leaves tiny scratch marks.

So they are basically like really really fine sandpaper. Only use them where that would be okay for you.