Here in NC we had an early version of pay-at-the-pump self-served gasoline stations in the form of unattended pumps with a dollar bill machine driving the pump. Not just any bill--only $1 dollar bills would work. There was no need for the machines to accept $5 and $10 bills simply because it was uncommon for anybody to purchase more than $3-5 worth of gasoline at a time. Plus, the crude dollar bill machines wouldn't make change, so you'd always "short" what you thought you'd need to avoid having to leave purchased fuel undistributed. Any time we'd be in the area of one of the "Star Flite" dollar bill stations, we'd circle through to see if any of the pumps had undistributed fuel available. We could tell by the readout--if it was not stopped on an even $ total, pop that nozzle into your tank and get some free gasoline. That worked often enough to justify the drive-through. Leaded regular in 1971 ran around 30 cents a gallon, and my '69 Impala had a 24 gallon tank.
Soon enough, somebody figured out how to rig a new and very strong dollar bill with a long strip of Scotch Tape doubled over and stuck to itself. On some of the dollar bill machines the rigged bill could be inserted, "click" to register a $1.00 purchase, and then slowly withdrawn by tugging on the strip of tape. Word spread fast when somebody "struck gold" and there'd soon be a line of guys filling up all grades of Camaros, Mustangs, Novas, Impalas, and Galaxies, all on a single dollar bill. We of course preferred 100 octane premium for such discounted purchases. I still feel kind of bad about that. Didn't take Star Flite long to put an end to that game, however, so I don't suppose it hurt them too badly financially.
Foy