Quoted from MrBally:Basically these machines (Besides Williams High Hand, Bally had Twin Joker and Joker's Wild) were "For Amusement Only" but meant for two players to shoot five balls apiece and each get a poker hand that lights up on the backglass. High hand wins a bet between players, Beer, a dollar ($5 these days, "It's only five dollars") etc.
I found a picture of my buddy’s Twin Joker with the Bally factory topper on it. Not the best picture, but...