I went "old school" and referred to my copy of "Gun traders Guide" 28th edition. Sometimes the info you need is not on the web.
500 ALS smooth bore slug version
500 CLD 20 gauge plain barrel (no rib)
500 EL .410 plain barrel
500 ELR .410 vent rib
500ALMR Heavy Duck magnum version (12 gauge)
500CLS 20 gauge smooth bore slug version
500BK 16 gauge c-lect choke
500 EK .410 c lect choke
500ATP8S law enforcement 8 shot
500ATP6S law enforcement 6 shot
500ATP6CN law enforcement 6 shot nickeled for marine use with pistol grip
500APR fancy wood, engraving, designated "Pigeon grade"
500 APTR trap gun Monte Carlo stock
There are likely more. That is most of them though.