Wuzhu coin issued by Emperor Xuandi

The inscription on this coin reads 'wuzhu', with 'wu' to the right of the hole, and 'zhu' to the left of the hole. Wuzhu means 'five grains', and refers to the weight of the coin (1 wuzhu = 5 grains = 4 grams). By coincidence, the size and weight of the wuzhu coin was the same as the Greek drachma and the Roman denarius.Wuzhu coins were first issued in 118 BC in order to stabilize the Chinese coinage by replacing banliang coins, which had become smaller and lighter during the early Han dynasty.It is estimated that over 28 billion wuzhu coins were made during the Western Han dynasty (206 BC-AD 9). As the Han empire expanded, these coins came to be used further and further afield. Wuzhu coins have been found in modern-day Korea, Vietnam and Chinese Central Asia. The wuzhu was probably the most successful Chinese coin ever, and continued to be used until AD 621, when it was replaced by the Kaiyuan tongbao coin of the Tang dynasty (618-906).