Yeah I was also assuming given my experience with arcade cabinets that you could substitute in a pushbutton for coins or a toggle switch to enable Free Play but no, it seems to want timed pulses from the feeder before it will indicate credits have been added so you would need some extra logic like a microcontroller.
Also yeah our bills got refreshed a few years ago. It's literally not paper anymore. It's plastic with a clear section to assist in preventing counterfeiting (and none of our vending machines accepted them for a while because of that). They're absurdly easy to stick together now but if you scratch and sniff the 100's they smell like maple syrup.
