Allow me to change the subject ever-so-slightly:
I have a 2230 that I'm about to re-cap, and the faceplate has a similar yellow discoloration as shown in the 250 photos, although not nearly as bad.
What's the cause, and how can I safely remove it w/o killing the lettering or worse? I know for sure that it's never been around smokers, since it was a gift from my brother-in-law, the original owner. I've had it boxed up since 1987.
I've very carefully tried mineral spirits, citrus degreaser for bicycles, even soaking it overnight in dish detergent. No luck.