Posts: 110
Threads: 24
Joined: Jan 1970
"its like some kind of oxidation with age or the abrasion of being slid in and out of its cover many many times"
It must depend on some other environmental conditions as well.
I have a 1981 USA-made HP-11C, one of the earliest models, it's been
taken in and out of its cover tens of thousands of times,
and it's still as new, no changes at all to the aluminum
bezel. In fact, it looks newer than any other HP-11C
I've come across, including two other more recent models
I also own.
No wear on the keys or key action as well, and it has
needed just 2 changes of batteries in 22 years, even with
heavy daily use. It amazes me no end !