Which retail technology was first widely implemented in military PX/BX systems before becoming standard in civilian retail?

The Post Exchange (PX) system has been a crucial retail element of military life for generations, providing essential goods and services to service members and their families worldwide. This retail network has evolved significantly over time, adopting various technologies and business models that often preceded similar innovations in civilian retail. Test your knowledge about this unique retail system that has served millions of military personnel throughout history.

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Universal Product Code (UPC) barcode scanning
Military Payment Certificates as an early form of closed-loop payment system
Self-checkout kiosks
RFID inventory tracking