Appendix F of the first edition AD&D Dungeon Masters Guide has rules and descriptions for gambling games that can be used in a campaign. Gygax included two ways to model a slot machine using standard six-sided dice. I was able to take this concept and improve on it. I have a set of dice with slot machine symbols on them.
I pulled these dice out during a Hackmaster campaign. The characters were in a city that had a large gnome population. The gnomes were specialists at making all sorts of magical and mechanical devices. The tavern that the characters were in had a slot machine. I passed over the dice and let the players wager their gold.
The dice themselves are white plastic six-sided dice. The symbols are printed on the sides. I acquired them in a set that contained 5 different dice games (poker dice, put and take, bowling dice, slot machine dice, and standard six -sided dice). The slot dice were a nice little prop to add some flavor to a standard tavern scene.