I sat next to a guy in the petrol pump business once on a flight from a time before time (pre-COVID), so I asked him how the pump knew when to stop: he explaine

I sat next to a guy in the petrol pump business once on a flight from a time before time (pre-COVID), so I asked him how the pump knew when to stop: he explained that the handle contained a rotating cylinder (halved in the middle) with a known volume V that rotated N times until V*N = Purchased Liters.