Nice purchase and pictures. I’ve considered getting one of those as part of my collection. I already have a Picturebook C1MVP (cripplingly slow but so pretty).
As for the BIOS, I looked on Sony Japan’s support page and didn’t find it. As the U3 was not in wide US release, finding information on it in English is pretty hard. If you happen to know a fluent Japanese reader, you might have them poke around some Japanese message boards like mobile01.com.
BTW, did you get any pics of the inside of the U3?