(RCSD) Help ID this Princess Diana / AIDS stamp

Hi,

I'm the fellow who runs www.aidsonstamps.com, the topical homepage for
AIDS on stamps. I'm about to add one stamp to our listings, but I
can't figure out what year or what the Scott number is. (I confess, I
don't have ready access to the Scott guides).

Can someone help me ID this stamp? It's part of a souvenier sheet.

http://store.coolstamps.com/imagesrv/882/410456398.jpg

I'm referring to the top-right stamp on the sheet.

Thanks!

--Aaron