There are tons of special printings on their cards, including things like you've noted and some of these.... A-xyz with all sorts of letter combinations; BG, BIN, BN, BNG and BINGO; BUS, CDS, CONV, EMP possibly followed by things like BINGO, LP, RV, etc.; PIT possibly followed by BINGO, LP, etc.; RV possibly followed by BINGO or SENIOR; SENIOR or SR possibly followed by BUS, BGO, BINGO, BUS, etc. and SLTS.

I'm not sure what the A-xyz cards are used for but I'm guessing the employee cards are used for machine access, maintenance, etc. like at other casinos.