Which innovative retail technology was FIRST widely adopted by military PX systems before becoming common in civilian retail stores?

The Post Exchange (PX) system has been a cornerstone of military life for generations, providing soldiers with essential goods and a taste of home while deployed. These military retail operations have evolved dramatically from simple sutler wagons following troops in the 1800s to modern, sophisticated retail environments. Test your knowledge about this unique retail institution that has shaped military culture and commerce for centuries.

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Barcode scanning technology (1974)
Self-checkout kiosks (1992)
RFID inventory tracking (1985)
Computerized point-of-sale systems (1981)