This was my Funhouse prototype game, serial number 2.  I got this game from an ex-Williams Lawyer in Chicago.  He owned it since 1990.  Differences:  ‘STEPS’ playfield with all 5-blue targets, different cabinet artwork with missing “Williams” logo, red lamp boards, some of the playfield plastics are different, wide Sys11 siderails, Rudy lid is larger, different mirror plastic, Diamond Plate playfield, and a SYS11 soundboard with WPC interface conversion board.  All the prototype games are stamped “Diamond Plate” but are not clear coated.  Williams was in a rush to build the first 15 games and they never got clear coated.  The sample games (about 200 of them) all are clear coated either by Sun Process (Diamond Plate) or by Linc Smith (LS Top Coat).