A member of these forums runs a mirror of the old SNK webbeh. I can't remember who or where, and I think it is incomplete, but if the NGPC section is there I remember catalogue numbers being displayed with title information...
and the archived page is:
<a href="http://www.personal.triticom.com/~erm/www.neogeo.co.jp/" target="_blank">http://www.personal.triticom.com/~erm/www.neogeo.co.jp/</a>
Thanks for all the help guys, Don't suppose you have the NEOP number for Mahjong anywhere, Can't see it on any of the lists, Is this also known as Koi koi mahjong or Dokodemo mahjong in Japan??