We all know how white/beige ABS plastic can turn yellow after years;
especially if it's exposed to UV (e.g. fluorescent) light.
Many generally thought that the only solution was to spray paint over
the plastic in the original color.
Well, there is another solution, called "Retr0brite".
See:
http://www.psfk.com/2009/03/retrobrite-open-source-problem-solving.html
http://retr0bright.wikispaces.com/
And, in particular, to make the stuff (it is not commercially available):
Now I wonder if I can do that with the number keys on an old HP-65.....
-John