1967 3M TEACH KEY Reading and Spelling. Scarce 3M EduPLAYtional game. Triangular shaped box. This game is in the same series as Egghead and Chicken. Includes 2 packs of 24 key cards (48 total), the house board, box, and set of keys. I do not know if add-on card sets were available, although it is possible. Players ages 5-8 insert the key into the correct missing letter hole of each word in order to correctly spell and thus unlock the word.