Just came across an MGM slot card that was never listed in the slot guide. Seems to fit between the 11th and 12th issues, listing 8 casinos on the reverse.

Scans of the new card are on the ChipGuide now
http://themogh.org/cgupdate/cg_showpic.php?pic=../cg_pix/nv/125464.jpg&picr=../cg_pix/nv/125464a.jpg