Why does rubbing a coin on steel make vending machines accept it?

How does the vending machine work? vending machine coin slot COin slot model SG-648 for vending Machine RO and other aplicant Widely use for vending machine Intelligent Micro-chip control, and high accuracy Tested vending machine slot It may just be that Vending machine coin acceptancerejection systems vary and some are much more elaborate than you would expect They don't

vending machine coin slot Coin Operated Vending Machine · Atlantis Classic 4 Lane Tea and Coffee Coin Operated Vending Machine · Initiative Coin Operated Vending Machine, Voltage : 150-