'Congo' was produced both as a complete game and as a conversion kit for narrow body WPC Security games. Designer John Trudeau said the gorilla in the lower-level playfield was sculpted by Stan Winston, the noted special effects and animation artist known for his work in television and motion pictures. Included in this listing is a prototype game purchased from a former Williams employee who in turn purchased the game from the Williams' 3401 California facility where it was setup in the lunchroom as a test machine. The current owner learned from Bill Grupp that its playfield is a prototype and the apron is one of only fifteen made. Here are its differences from the production game: 1. The apron is a lighter green 2. The inserts leading to the left ramp are 3-2-1 instead of M-A-P. 3. The yellow arrow insert for the upper right saucer does not say 'Video'. 4. The yellow insert pointing up the volcano ramp only says 'Collect' instead of '3X Collect' 5. The scoops for the saucers are silver instead of black. 6. The insert closest to the lower saucer says 'See Map' instead of just 'Map' and is purple instead of green. 7. The 'Skill Fire' insert is green instead of purple. 8. Red circuit boards all underneath the playfield. This test game is in a No Fear cabinet and still has the NF artwork on the backbox, but the lower cabinet is decaled with Congo. It has the WPC 95 boardset. It has the new style speaker grille but with the old style light board, not the shadow box style that the production games have. Also has production wire ramps, not black or unplated like some prototypes. Possibly these ramps, as well as the grille, were changed for the employee who bought it: Bill Grupp had indicated that employees who purchased such games tried to make their game as nice as possible before taking them home.