premise: Game Plan was a pinball manufacturer that produced pinball tables from 1978 to 1985. Game Plan was a subsidiary of AES Technology Systems and was located in Elk Grove Village, Illinois. Game Plan's president was former Chicago Coin table designer Wendell McAdams.
hypothesis: AES was located in Chicago, Illinois.
reason: AES was located in Elk Grove Village, Illinois. Unless Elk Grove is a part of Chicago I'm not sure how the system missed this one.