When I was in high school I got a job pumping gas at a Flying "A" station (anybody remember those). We gave out Green Stamps with every purchase. The Shell station across the street gave out Blue Chip Stamps in a like manner. Every year the Shell station would invariably start a "gas war" and prices would drop like a rock. We were normally selling gas back then at 21-23 cents a gallon. But during "gas war" season the price would often drop as low as 18 cents. Then someone over at the Shell station came up with the bright idea to also give away more "stamps" to attract customers. I mean we're talking about 20X, 40X,50X and even 100X. Everytime "they" upped the ante we, of course, had to follow. My mother loved it. Our local Green Stamp store (yes, there really was such a thing) was overflowing with customers redeeming their books of stamps. 

Across the pond we had a version which copied the USA - Green Shield Stamps:

https://en.wikipedia.org/wiki/Green_Shield_Stamps

For a bit of "pocket money" and the experience - I already had a full time job at BAe at the time. I got a part time job in a local filling station attached to a car dealership. The petrol pumps were self service so all I had to to was be a shop assistant  which did involve closing up at the end of evening shift.

They offered Green Shield Stamps - many customers didn't bother with them which if course meant a nice little earner for us behind the till. According to the machine about 99% of our customers collected the stamps . Yes, I'm not proud of it now, and karma dictated that I had a sore tongue from binge licking the stamps to fill up a book or two  Another perk was that we could go and use the hot drinks machine in the car showroom!  So sometimes one or two friends also dropped in to say hello. It was a Lada dealership BTW.. Hey! they were new, and sensible and worked! 

One thing I AM proud of is that during my time there I met my wife - married for 29 years now. She was the friend of one of the other assistants. 

Boy, do I ever wish my job was at a self-service station. There I was, 16-years old wearing this dumb-looking green uniform with a stupid hat to match. Pumping the gas (petrol), checking the air pressure in each tire (tyre), opening the hood (bonnet) to check the oil level and inspect the radiator hoses for leaks, and washing the windshield (windscreen)........ON EVERY CAR. I'd do that for three hours everyday after school and seven hours on Saturday. The only exceptions to that routine were the days I'd get a call from my boss early in the morning asking me to skip school and open the station because he was too hungover from a night of drinking to even try to go to work. But, that was early-on in the Fabulous Fifties so at least I could have some decent music on the radio while I worked (you could even understand the words). The times they are a changin'........