Chicago: The Simplicity Co., 1908. A 3 1/4" x 6" card folder with an image of a schoolmaster pointing at 13x13=? on the black board with 3 perplexed and 1 "bright" child ready with the answer. He holds the Lightning Multiplier in his hand. The right end of the card has an index with 25 vertical numbers front and back. The same, but horizontal index crosses the top of the paper slide card within. As the card is pulled out the answer to the multipliers becomes easy. The reverse has an index from 26 to 50.