Ok, so, as I said, I bought myself a Sony Clie PEG-SJ30.
Just for good habit, I decided to go to Sony's website and check if there were any updates on the software for it, or whatever.
Mine is a PEG-SJ30/U model. Sony has never heard of it. If you check for it in Sony's product support DB, it says it's a bad model name.
Everywhere you gonna find pictures of the PEG-SJ30 and will see a silver-plastic case.
Well, mine has a teal-and-black plastic case.
The one you see everywhere has a flip-top nylon screen cover.
Mine has a (sony original) book-shaped leather cover (I don't like it, it's way too thick).
Oh, sure, it exists, you can find it in google, but it seems it's a very unusual model. It works great, though.