Probably pre-1974.
In the late '60's, I kept my tank pretty much full when I worked at a gas station.
Once I pumped for the customer (and did the oil check, cleaned the windshield, etc.) and he drove away, I would drain the hose into a 5 gallon can I kept on the pump island.
I could usually fill that can about three times a week.
Back then, the hose handles had a pop-off type of valve, but there was no valve at the actual pump...the only thing that kept all the gas from flowing back into the underground tank was the pump rotors and the metering device.
It would eventually flow back, if left alone, but the gas in the hose was still there.
That's why you would hear the pump whine sometimes after it was activated...it was filling the hose beyond the pump rotor.
The owner knew I was doing it...he didn't care, as the metering device didn't register anything beyond itself to the handle valve unless the pump was actually running.
EPA and OSHA took care of that when the fuel crisis hit.
Thanks for that. Interesting. My dad told me about those valves when I was trying to drain the hose. He also told me that way back some pumps would already have several cents on it because of the gas left in the hose.