Yes, it does look like data has been burned to the disk. I don't know how the spec differs between full-size and 8cm DVD, but there must be
some difference, since this
spec page for my DVD player clearly seems to indicate that miniDVD is NOT supported, for whatever reason.
Incidentally, when I insert the disk in my Power Mac, the Finder tells me to initialize, eject, or ignore. I usually press ignore, but the Finder does not mount the disk. I can, however, go into apps like Disk Utility and Toast and "see" it (Toast and a few other "burning" apps refer to it as rdisk1, which I can only assume means RAM disk). I don't think this really helps much as I haven't been able to get past this point (i.e. trying to record from the disk in order to make a copy to burn on a "real" DVD always fails - but this makes sense if the system registers it as a RAM disk).
What do you think would happen if I pressed Initialize? Normally, initializing completely erases the disk, but I don't think that would happen with a DVD-R. Even so, I don't want to put the data on these disks at risk.... Thanks for your continued time.