Ban Liang

The ban liang ("half liang") is a round bronze coin with a square hole, issued by the state of Qin and then made the standard coin of the whole of China after the Qin unification in 221 BCE. Its name refers to its nominal weight of half a liang, or 12 zhu, and it is inscribed with those two characters in seal script on either side of the hole.

The ban liang was the first coin to circulate across a unified Chinese empire. The early Han dynasty continued to cast it, at progressively lower weights, until it was replaced by the wu zhu in 118 BCE.

Qin was one of several Warring States casting round coins, known as huanqian. Han historical records state that Qin began issuing coins in the reign of King Huiwen, in 336 BCE, and ban liang pieces are widely attributed to Qin from the later fourth century BCE onwards. Pre-unification Qin ban liang are often large and irregular, with weights that vary widely from piece to piece.

After the First Emperor, Qin Shi Huang, completed the conquest of the other states in 221 BCE, his government introduced standard weights and measures, a standard script and a standard currency. According to the historian Sima Qian, the Qin recognised two forms of money: gold, used for large payments and measured by weight, and the bronze ban liang for ordinary transactions. Other objects that had served as money, including cowrie shells, jade and pearls, lost that role.

This meant the end of regional forms such as spade money and knife money. A single bronze coin, recognised throughout the empire as legal tender, helped the state collect taxes, pay officials and soldiers, and integrate markets across a very large territory.

The ban liang is plain: round, with a square central hole, two characters and no raised rim. It was cast in moulds rather than struck, which allowed large numbers to be produced but resulted in noticeable variation in size, thickness and weight. In practice, few surviving coins match the nominal 12-zhu standard exactly, and even official Qin issues varied considerably.

The Han dynasty, founded in 206 BCE, kept the ban liang name but cut its weight. Early Han coins were often very small and light, earning the nickname "elm-seed" coins. The government experimented with several weight standards, and in 175 BCE Emperor Wen fixed the coin at four zhu while still using the old "half liang" inscription. He also allowed private individuals to cast coins, which led to great fortunes for some casters and to widespread variation in quality.

The gap between the name of the coin and its actual weight is an early example of currency debasement, and the profit from casting lighter coins was a form of seigniorage. Lighter coins and uncontrolled private casting contributed to price rises, a form of inflation that worried Han officials.

Under Emperor Wu, the Han court reformed the currency several times and in 118 BCE introduced the five-zhu wu zhu coin, which became the lasting standard. Private casting was later banned and minting centralised in the capital.

The ban liang nonetheless set the pattern for Chinese money for more than two thousand years. Its round shape with a square hole, cast in bronze and threaded in strings, carried through the wu zhu, the Tang kaiyuan tongbao and Song dynasty coinage. The Qin decision to unify the currency also stands as an early example of a state using money as a tool of political unification, a theme that recurs in later monetary history.

• British Museum – Collection online
• American Numismatic Society