"He gave me this. A consolation prize. A piece of his paper currency."

Economy James Surowiecki of ieee Spectrum considers the history of money:

"In the 13th century, the Chinese emperor Kublai Khan embarked on a bold experiment. China at the time was divided into different regions, many of which issued their own coins, discouraging trade within the empire. So Kublai Khan decreed that henceforth money would take the form of paper.
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"It was not an entirely original idea. Earlier rulers had sanctioned paper money, but always alongside coins, which had been around for centuries. Kublai’s daring notion was to make paper money (the chao) the dominant form of currency. And when the Italian merchant Marco Polo visited China not long after, he marveled at the spectacle of people exchanging their labor and goods for mere pieces of paper. It was as if value were being created out of thin air."