You're kidding, right?

Seriously, certain grocery stores, gas stations, and other merchants for years gave out savings stamps with your purchases (S&H, Top Value, and Family Stamps come to mind), usually one stamp for every $0.10 spent. We pasted these stamps into "books" (50 to a page) and redeemed them at special centers or by catalogue for merchandise--hand mixers, sleeping bags, you name it. They were mostly discontinued in the late '70s, IIRC, replaced by "double coupons" and other store promotions.