Which retail customer experience innovation was first widely implemented in military PX stores during the Vietnam War, fundamentally changing how deployed service members shopped?

Military exchanges and post exchanges (PX) have been vital retail operations serving armed forces personnel and their families for generations. These unique retail environments have evolved dramatically over time, from simple commissaries to modern shopping complexes. This poll explores a significant customer experience innovation in military retail that changed how service members shop while deployed.

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Self-service shopping format replacing counter service
Military credit card system (precursor to modern military star cards)
Mail-order catalogs with overseas delivery guarantees
Standardized pricing across all global military installations