If someone can post a pic of their rear seat so that I can compare it to one I have sitting in the garage then I might be able to help you.
Sounds odd but I cought a Y2K RSV in the summer that the seller had a pillion seat for but it clearly isn't from a Y2K, nor does it look like the one I remember having on my '02 RSV a while back.
The only thing I think it must be is from an '03 but wouldn't want to sell it without knowing for certain!
Cheers
Jon