A Pachislo slot machine is an authentic Japanese gaming machine used in Japan casinos parlor. Pachislos operate on tokens rather then coins. This is because gambling is illegal in Japan. These tokens can be exchanged for prizes.
One reason surely is that it's Japan's one legal outlet for gambling, allowing players to try their luck and win money playing pachinko. In fact, during Japan's long economic downturn many turned to pachinko in a last ditch effort to make ends meet.
