Which retail innovation was first widely implemented in U.S. military PX (Post Exchange) stores during the Vietnam War era to boost morale and modernize the shopping experience?

Military Post Exchanges (PX) and base retail operations have evolved dramatically over the decades, transforming from basic commissaries to sophisticated retail operations. These innovations have significantly impacted military life and morale throughout history. Test your knowledge about how military retail operations have innovated to serve personnel across different eras and conflicts.

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Self-service shopping format (replacing counter service)
Electronic inventory tracking systems
Barcode scanning at checkout
Credit card payment acceptance