The original Concentration rebus board, like many game show sets of the mid-20th century, was electromechanical. It used 30 trilons, or three-sided blocks. On one side of each trilon was a numeral for the contestant to call. Another side had the name of a prize, or FORFEIT | TAKE | WILD CARD. The third side had a portion of the rebus. As you might imagine, the rebus was painted on plywood and cut into 30 rectangular pieces, which stagehands installed behind the board.
Art James once witnessed a near-disaster involving Bob Clayton. James was working on The Who, What or Where Game when he smelled smoke coming from the Concentration studio. Moments later, he heard Clayton yelling for water. The rebus board had caught fire, but it was just an electrical fire. Steve Ryan records James’ punchline: “Poor Bob was the first emcee that I knew who hosted a game show that almost went up in flames!”
Jack Narz had troubles with his set, too. He told Ryan about the temperamental board: “Many times when a contestant called two numbers the rebus blocks would rotate and keep rotating ... revealing part of the puzzle. This would continue until our director had to yell ‘CUT!’ We never had a fire like [the one Clayton had]; however, we did come close a few times!”
Classic Concentration took a cue from Alex Trebek’s other game show, Jeopardy!, and used Sony monitors for its “board” (which was reduced to 25 panels for faster play). The red-on-yellow numerals appeared on one monitor, and the prizes were on a separate blue-screen monitor (the blue areas were replaced by parts of the rebus). This arrangement allowed games to be set up in less time, and the equipment was far more reliable. The contestants saw the entire “board” — rebus and all — on one 30-inch monitor.