Large scale international trade relied on standardized forms of money for thousands of years before the first coins were minted: https://www.pnas.org/doi/10.10

Large scale international trade relied on standardized forms of money for thousands of years before the first coins were minted: https://www.pnas.org/doi/10.1073/pnas.2105873118 https://www.pnas.org/doi/10.1073/pnas.2105873118