Jiaozi promissory note from the Song Dynasty. The earliest jiaozi were issued in Sichuan province by merchants to relieve their fellow merchants of the high costs of transporting the heavy government-issued iron coins.pic.twitter.com/L6NSX1nPnA
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Jiaozi generally weren't redeemable in grain, it's probably being used as a symbol of wealth, and to show the merchants in a situation where they would use the notes (buying/selling grain.
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