The term "stamp" in this context is used to refer to a system of payment using a proof-of-purchase (the stamp). Another example, a postage stamp is evidence tha

The term "stamp" in this context is used to refer to a system of payment using a proof-of-purchase (the stamp). Another example, a postage stamp is evidence that you have paid for the delivery of your letter. Some countries use stamps to pay for government services like deeds or passports. You are confusing this with a ration system using stamps, which allows the purchase of a good, but does not actually pay for the goods.