The high end dealers may hire off duty police. They pay the local police department & the police department pays their police officer. He is actually on duty in this case but the officer is probably working overtime. It is rare to see uniformed police on the floor like this but they are present at some shows. Many shows have their own security personnel on the floor in plain clothes. I know one guy that works security at Westchester NY and he is also a paper money collector. I've also seen flashlight cops (that might be worthless in a serious situation) guarding doors . My only advice might be for you to contact the show organizer & ask them specifically what you might do to become involved with the specific show.