No – mechanisms for rejecting bad coins were pretty standard on most vending machines by the 1960s.
Having locks that could easily be opened was something else.
But hacking the vending machine with frozen stuff that would melt and evaporate was higher tech and way cooler than using a coin on a string orsome foreign coin that worked well in the machine or any of the standard cons.
Some of the pinball machines could be convinced to give free games with a paper clip. And I’m using the original definition of hack, which usually had nothing to do with computers. The goal was to get free games, not to steal money from the machine. I never played the things myself, having grown up in NY when they were outlawed.
One of the really common things these kids almost certainly did was hack free long distance phone calls. That’s was going on all over the place in the 80s. But I can see something that realistic and not difficult as something the filmmakers probably avoided filming. Too close to what people really did. People like Steves Jobs and Wozniak. They referred to it in “WarGames”, though, so who knows?
John Draper discovered through his friendship with Engressia that the free whistles given out in Cap’n Crunch cereal boxes also produced a 2600 Hz tone when blown (providing his nickname, “Captain Crunch”). This allows control of phone systems that work on single frequency (SF) controls. One can sound a long whistle to reset the line, followed by groups of whistles (a short tone for a “1”, two for a “2”, etc.) to dial numbers.
If they ever make a Mount Rushmore of actors who played 80’s movie assholes, William Atherton belongs right up there. Real Genius, Ghostbusters, Die Hard – the man just had a genius for playing self-important, antagonistic jerks. I respect him tremendously.
Paul Gleason and William Zabka belong up there as well, I’m not sure who would be the fourth.