The Sui Wu Zhu had the distinction of bringing to a close the longest circulating Wu Zhu coin in ancient China's numismatic history. Wu Zhu coins first came into circulation during the Han Dynasty 206BC - 220AD. Some Sui Wu Zhu coins were minted in tin or lead alloy. Such coins are lighter in weight as compared to those minted in bronze. The coins from the Sui Dynasty were of high quality with strong calligraphy inscriptions.