I looked at the entry in Discogs for catalogue number IMCD 191; that seems to be an earlier PolyGram pressing with code PY on the back cover, and a sticker for the catalogue number, and showing 1990, so I suspect the copyright date was used again. Going through the other IMCD numbers in Discogs, copyright years seem to have been used for most of the ones that don't say "unknown", but the Nick Drake compilation IMCD 196 is dated 1994. I then went to one of my R.E.D. (formerly Music Master) catalogues, which has July 1994 as the date for IMCD 191, so I am going to submit a correction to make that the date (yours would still be a 1998+ pressing, though, because Universal didn't take over PolyGram, including Island, until late 1998-early 1999).
This album was first issued in 1990, but I think this Island Masters version is a later reissue, the giveaway being the UN506 distribution code on the back cover, which signifies Universal, so a 1998 or later issue.