Toy Tinkers (also known as the Tinker Toy Company), based in Evanston Illinois, entered the yo-yo market in the mid 1950's with their Toy-O-Ball series. Faturing a rewinding metal reel housed in a round plastic shell, these yo-yo balls looked very simmilar to the HEP Magic String Balls sold during the same period. These yo-yos were produced as baseballs, basketballs and footballs. It is unclear as to whether Toy Tinkers produced the HEP line or vice versa. The Toy-O-Balls were the first auto-returning yo-balls to be produced.