Chris Moore from Tokens Only recently posted some intriguing documents he stumbled across -- specifications for anti-cheat devices used with coin-operated games. Apparently, manufacturers designed a variety of these for their different coin mechanisms and coin door configurations to outsmart the criminal kids trying to play their games for free.

The pages detail "anti-penny, anti-nickel, anti-stringing, and anti-wire modifications or mechanisms" that operators could use -- protections that would've easily defeated my washer-on-a-string trick that actually worked for me a few times.

You can see the documents, including a service bulletin from Coinco and an article in Franks Crank's ("How to stop 'quarter stringing', 'penny flipping', 'nickel rolling', 'penny rolling', 'wire cheating', and coin-door banging..."), at Tokens Only.