The Sesame Street Magic Numbers Set is a 1988 Sesame Street Colorforms set. Text on the box promises, "Here's a fun way to magically learn your numbers with Colorforms' plastic 'tricks'. Little magicians can count objects and see them turn magically into the right number."
Each trick is a piece printed in red, black and white, with a picture of objects to count -- three keys, four monsters, seven balloons, etc. When the piece is viewed through a sheet of red film, a young magician can count the number of objects. Twisting a knob to move the piece under a sheet of green film, the magician reveals the correct number.