The Harry Potter Collector’s iPod was originally released in 2005, as a 4th-generation iPod with color display to mark the release of the debut of Harry Potter audiobooks on iTunes.
The iPod was engraved with the Hogwarts crest on the back, and was revved to a 30 GB, 5th-generation iPod shortly after release.
Coincidentally, I remembered just recently that this particular special edition iPod existed. It carries model number MA215LL/A and only occasionally seems to crop up on eBay. I could find very few photos of it, one of which is on a fantastic Polish “iPod museum” site, and another in a MacRumors thread.
In trying to find photos of that, I came across some more collector edition iPods which are arguably even harder to find, each engraved with the signatures of Beck, Madonna, or Tony Hawk. There was even one engraved with the No Doubt logo.
I don’t know anyone who bought any of these special edition iPods, aside from one friend who bought a U2 one because it was the only way to get a black iPod at the time. I imagine that only a handful of any of them were produced.
As best I can tell, the celebrity engraved set of iPods were all made available only around Christmas in 2002. But Apple didn’t give up on limited editions with those ones, or the Harry Potter ones, or even the U2 model. The most recent special edition iPod that I can find is the stainless steel Shuffle, released in 2009. And if you have one of those and kept it in good condition, you can sell it for a mint on eBay — I’m seeing prices starting at nearly $800 Canadian. For what it’s worth, that’s about a seven-fold return on investment, performing about twice as well as Apple’s stock in the same timeframe.