Which major retail innovation was first widely implemented in Army Post Exchanges (PX) before becoming standard in civilian retail stores across America?

Post Exchanges (PX) and Base Exchanges (BX) have been vital retail operations supporting military personnel and their families worldwide since the 19th century. These unique retail environments offer tax-free shopping and help fund morale, welfare, and recreation programs on military installations. Test your knowledge about this specialized retail system that bridges military history with consumer commerce!

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Self-service shopping (customers selecting their own merchandise without clerk assistance)
Loyalty card programs with point accumulation
Barcode scanning at checkout
Drive-through pickup windows for pre-ordered merchandise