Which technological retail innovation was first widely implemented in military Post Exchanges (PX stores) before becoming standard in civilian retail?

The Post Exchange (PX) system has been a cornerstone of military retail for over a century, providing essential goods and services to service members and their families worldwide. This unique retail ecosystem has evolved dramatically from its humble beginnings to become a sophisticated retail operation with billions in annual sales. Test your knowledge about this distinctive military retail innovation that bridges civilian consumer culture with military life.

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Universal Product Code (UPC) barcode scanning systems
Self-checkout kiosks
Customer loyalty card programs
Electronic shelf labels