From Marvin's Marvelous Mechanical Museum in Farmington Hills, Michigan (which is a hoot to visit!):
Patented in 1939 as a vibrator to relieve sore feet:
The Exhibit Supply Company of Chicago made at least 360 different machines starting in the 1920's, including The Six Shooter, The Love Tester, Nudist Colony and Atomic Laugh Bombs. The company was started by J. Frank Meyer in 1900 making printed material used by the carnival trade, and later specialized in exhibit cards which buyers could acquire from a coin dispenser. For more information, visit the International Arcade Museum and Interesting Exhibit Cards.