I suspect that skin oils and prior cleaning may contribute to the breakdown of labels. When I have cleaned my 45, 65, and 67 with dilute isopropyl, I think I got lucky, but the HP80 spooked me.
Randy of FixThatCalc.com has recommended light soap and water at most. Others here have said don't even attempt to clean unless the unit is irretrievably dirty.
The Classics and Woodstocks seem especially vulnerable to this--silk-screening on plastic doesn't say "durable" to me, at least not in the sense of surviving decades of heavy use in the hands of previous owners who don't cherish these things like we do. The lettering on the metal keypads of the Spice, Pioneer, Voyageur, and 48G/GX/S/SX looks a little more avid to me, but after the HP80 horror show any future cleanings for me boil down to the classic Clint Eastwood question "do ya feel lucky?"
At least I know that if lettering fades on any of my calcs I can make perfectly serviceable overlays so I can see at least what the lettering is supposed to say! That HP-80 has been cosmetically flawed, but with help from here and a little ingenuity I have been able to restore it to full legibility and usability. I was playing with it just tonight. Didn't have the heart to until I got that overlay on.
I have a 34C that is a 1980 model but feels light in the hand, certainly lighter than the 1980 33C. I hope to heavens I got an early version of one of the "good" 34C's. I know the 15C eclipsed the 34C entirely, but I really love the twinkly LED as it labouriously Romberg's its way thru an integral :)
Les
Edited: 15 Feb 2007, 5:55 p.m.