Gumball machines always have simple mechanical coin validators. It can often be used with a circulation coin or similar sized token. This allows to operate the gumball machine as vending machine as well as dispenser for free give aways.
Gumball machines are often located in supermarkets, shopping centres and amusement parks where they may not want money in the machines to avoid burglary. Operating the gumball machines with tokens solves this problem.