They called them "trade stimulators" because gambling was illegal and they couldn't very well call them "slot machines". They are, however, basically a slot machine that gives you a gumball, or some other small item, everytime you put money in and pull the handle. Most paid off in other ways, with points, prizes or money, for certain combinations on the reels. If the authorities came in, they were either hidden quickly, hence the small size, or the owner would just say they were selling gumballs or whatever. Hope that explains it a little bit. Doug