Gene, I'm guessing it might stand for Harolds Club Gun Club, seems to me the roulettes were marked "HC".

Just a quick look in Kling/King's book,A family Affair, brought info from a gal who was a dealer at the Gun Club from time to time. she says they had six or seven 21 tables and a crap table that the shooters would gamble at when they weren't shooting. Goes on to say that the tables were only open during shoots and they had about three major shoots a year. Just skimming the chapter, there seems to be roulette and slots added during the years the place was open. Haven't gotten a chance to read any of the book yet, got Harrah's bio by Mandel yet to start.