Wow... Complicated issue!!!
The Woz iBook states that
[...] Apple's polycarbonate coating is itself fairly impervious [....] (Emphasis added)
That suggests that my iBook's lost finish/gloss is the result of a chemical reaction that scoured off its polycarbonate coating and that the best polishing may do is impart some shine to the under-case.
It occurred to me to call the issue in to AppleCare as affecting my (covered) MacBook (which appears to be made of the exact same material as the iBook), and although the tech's best suggestion was, understandably, to bring it to a Genius for a look-see, he tended towards the same thought I expressed in the previous paragraph.
I also took a look at recent eBay sales of iBooks similar to mine to try to get an idea of how much I might realize from a sale and found that it wasn't likely to be enough to justify my getting involved with ordering and testing expensive (not necessarily, but after delivery...) polishes, so I've decided to give the Turtle Wax suggestion a go...cheap, and available pretty much right around the corner.
More to come...
Thanks to everybody who's contributed input.
