reply to u/remy_vega at https://old.reddit.com/r/typewriters/comments/1wxj0js/olympia_sm3_i_think_acquired_now_to_cleaning_and/
The white material is likely oxidation/corrosion specific to the metal on the piece. I'd guess potentially zinc oxidation. Duane has used lacquer thinner on stuff like this in the past with good results. (See https://www.youtube.com/watch?v=hDpTJ4NQGwk).
However for the material on the keys, you're likely to damage the plastic on them. For this part you could spot test some vinegar as a means of removing the oxidation without damaging the keytops. Try it out on one key to see how well it works. If it helps, you can remove the keytops individually. (See: https://youtu.be/XRm0VH42y1s?si=P0D1L9bm8uMRSJDC&t=867) I might also try a thin/skinny brass bristle brush either before, or in combination. (See: https://boffosocko.com/2024/12/01/typewriter-tools-upgrade/#Typewriter%20Cleaning%20Tools)
See another occurrence at https://reddit.com/r/typewriters/comments/1x2drma/olympia_sm2_restoration/ where kizeer reported success at my method by saying:
Thanks for the links! I started to remove the key caps and soak them in vinegar and brush the rest off which seemed to work fine. Just having some issues to remove the first row of key caps (1,2,3,..). I guess I need to remove the case/housing first.