Leave it to Joe Porper to solve many of the problems of contemporary coin benders. When we saw Joe perform folding money at our recent trip to the Magic Castle, we laughed at how devious the method was! It's that ingenious!
You talk about "What's folding money? It's paper money, but what's NOT folding money are coins."
As you speak, you bring out your folding money... a few bills in a money clip. "Do you have any non-folding money, say a quarter I can borrow? And just to make sure I don't do a switch or anything, I'd like you to mark your coin with this pen, mark it in any way you wish... so that there is no question that this is your coin. There is no other coin just like this one anywhere in the world.
"One of the problems with many coins, when you want to use them in, say, a vending machine, is they don't work. You always wonder 'Why', well, the reason is they are bent, they won't fit in the coin slot and they often get stuck and you lose them.
"Do you know how they get bent? I do, let me show you." You drop the marked coin into the folds of your folding money, as you say, "Your coins often get mixed in with your folding money, and if I give it a little squeeze, just watch, and it drops out bent!"
Indeed it does, and it is their coin; there is no switch and it is really bent. Your spectators have just witnessed the unbelievable, spectacular, impossible phenomena of bending a quarter with the power of the human mind!