Which retail technology innovation was first widely implemented in military exchanges (PX/BX) before becoming common in civilian retail stores?

The military exchange system (PX/BX) represents one of history's most unique retail chains, serving military personnel worldwide for centuries. These stores evolved from simple sutlers' wagons following armies to sophisticated retail operations. Today's modern exchanges incorporate cutting-edge retail technology and inventory management systems while maintaining their distinctive mission of supporting military communities. Test your knowledge about this fascinating intersection of military history and retail operations!

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Standardized universal product codes (UPC barcodes)
RFID inventory tracking systems
Catalog kiosks with home delivery options
Self-checkout stations