When there is the chance at a fast buck, you will find the unscrupulous – people who look at cheating slot machine games, or trying to fool the casino, or those who sit on street corners performing three card trips.
The old mechanical slots gave plenty of opportunities for potential scammers to try their thing. The classic scam was the string and coin, where the player would put the quarter on a string, attempt to insert it into the pay slot and whip it out quickly, in the hope that a credit would be registered without the 25c making it into the bowels of the pay box.. Get it right and you could get enough free credits to try to make a profit. It was the eternal way to get free play!
This method has obvious draw backs that soon made it unworkable. The first was being caught red-handed in a casino with a coin on a piece of string mid-way down a slots 918kiss.. It’s very hard to explain your intentions at this point without the security staff coming to one conclusion – that you are trying to rip them off. Expulsion and blacklisting soon follow at this point.
Those spotted sometimes got the nickname of Yo-yo players for the obvious reason of the string bouncing up and down.
The second problem was that a simple change is slot machine design made the string and coin obsolete. A simple one way gate on the way down the funnel to the collecting box meant that coins couldn’t be reclaimed, even by a lightning quick pull on the string.