Which innovative retail pricing strategy was first widely implemented in military Post Exchanges (PX stores) during World War II that later became standard practice in civilian retail?

The Post Exchange (PX) system has been a crucial part of military life for over a century, providing essential goods and services to service members worldwide. These military retail operations have evolved from simple commissary stores to comprehensive shopping centers, employing unique pricing strategies and customer loyalty programs. Test your knowledge about this distinctive military retail institution that has shaped the shopping experience for generations of military personnel and their families.

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Self-service shopping (customers selecting their own merchandise without clerk assistance)
Manufacturer's suggested retail pricing (MSRP)
Buy-one-get-one-free promotions
Seasonal clearance sales