Wu Zhu

Wu Zhu (Chinese: 五銖; pinyin: wǔ zhū) is a type of Chinese cash coin produced from the Han dynasty in 118 BC when they replaced the earlier San Zhu ("Three Zhu") cash coins, which had replaced the Ban Liang (半兩) cash coins a year prior, until they themselves were replaced by the Kaiyuan Tongbao (開元通寳) cash coins of the Tang dynasty in 621 AD. The name Wu Zhu literally means "five zhu", with a zhu being a measuring unit officially weighing about 4 grams; however, in reality the weights and sizes of Wu Zhu cash coins varied over the years. During the Han dynasty, a very large quantity of Wu Zhu coins were cast, and their production continued under subsequent dynasties until the Sui.

The production of Wu Zhu cash coins was briefly suspended by Wang Mang during the Xin dynasty, but after the reestablishment of the Han dynasty, the production of Wu Zhu cash coins resumed. They continued to be manufactured for another 500 years, long after the fall of the Eastern Han dynasty. Minting was definitively ended in 618 with the establishment of the Tang dynasty. Wu Zhu cash coins were cast from 118 BC to 618 AD, giving them a span of 736 years, which is the longest for any coin in human history.