The "Secret Category" questions were always single-part, which is why that square would always be in an outside box. The show's producers knew, even from the very beginning of TTD on NBC in 1956, that if a player captured the center box on the board, he would eliminate four of the eight ways his opponent could beat him.
Hence, the center-box questions were always made more difficult than the outside-box questions (two-part questions, in fact, from 1978 on) and also worth more money than the outside-box questions. Here's the breakdown:
NBC daytime version (1956-59): Outside-box questions worth $100, center-box questions $200.
NBC prime-time version (1957-58): Outside-box questions worth $300; center-box questions $500.
CBS daytime version (1978): Same as the NBC daytime version.
First syndicated version (1978-86): Outside-box questions worth $200 (except for "Secret Category" and, I seem to recall, a special occasional "Add A Grand" category that was worth $1000); center-box questions $300.
Second syndicated version (1990): Outside-box questions worth $500; center-box questions worth $1000, unless players had previously tied one or more games. In that case, those amounts were multipled by the game number the players were playing. ($1000/$2000 if they were playing their second game after tying their first game; $1500/$3000 if they were playing their third game after tying their first two games, etc.)
Michael Brandenburg
(But one of the things I didn't like about TTD's mercifully short-lived 1990 version was that if the players tied, the prize pot was wiped out after each tie and started over from zero for the [next] tie-breaking game. I would have much rather had the "carryover pots" from the previous versions of the show after ties.)
