Norm (the 34C zealot) inspired me to get back to the one HP LED unit I've got: a beat-up HP-97 that I wasn't sure would work again.
In fact, though, it was the battery pack which was the problem, and after rebuilding it (actually, after stuffing four Radio Shack sub-c's into the plastic housing) and charging for a bit, it works wonderfully!
During the process of cleanup, I used "Armor All" to un-stick the "form feed" button, and to generally clean up and treat the exterior, after using enamel paint thinner to remove some dried-up old tape stickum that was visible in places. The result looks fantastic! While there are certainly a few dings & scratches, the finish looks brand new-ish.
But (only) then I got to wondering -- is a protectant like Armor All really a good idea, long-term? Does anyone have an opinion or relevant experience?