I bought these Celtic postage stamps in June 2003 on ebay from a New York dealer. They are crackers and show they are issued in Grenada. At the foot of the sheet is "Distributed and designed by Victory Cards" .."2002" "copyright Action Images plc". I don't imagine for one minute they are officially backed by Celtic so copyright in this case means little.
I bought these postage stamps (below) from a dealer I think about 2004. They are on football in Sweden and bottom left shows Henrik Larsson.
The set of 4 Eire Stamps below come from Celtic collector John McMahon. The 2nd from the right shows Roy Keane. The right hand stamp shows Packy Bonner. Again I have no date of issue for the stamps.