Why are Bottle Caps the Currency of Fallout?

With the twist of a Nuka Cola or the crack of a Sunset Saspiralla, any Wastelander can obtain currency in the form of its bottlecap. But why did the Fallout Universe settle on bottlecaps as the main form of currency in the Wasteland? Well in exchange for 8 minutes and 31 seconds of your time - you can find out here.

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