It has been devalued and cannot be exchanged in kind.

Copper coins, ancient copper coins. During the Spring and Autumn Period and the Warring States Period, with the development of commodity economy, the metal weighing currency that needs to be divided and identified in circulation gradually became unsuitable and was replaced by metal coins. Most ancient coins in China were cast in the form of copper alloy, and square hole coins (copper coins) were the most common ancient coins.