OTOH, and I have hit this in another thread, when I lived in IL I have a FOID that had across the top, prominently, "ILLINOIS STATE POLICE" and under that "Firearms Owner Identification". I was flying somewhere and the girl at check in (way before TSA days) insisted on seeing two forms of picture ID, so since I had only my IL DL and my FOID, I showed her my FOID, at which point she asked me if I would be carrying a gun on that trip.
I understand IL has changed the format of the FOID so it doesn't appear to be a State Police ID.