In 221 BC, Prince Zheng of Qin succeeded after many years of warfare to unite the diverse Chinese feudal states under his rule. From then on he called himself Zheng Qin Shi Huang: First Sovereign Emperor of Qin (until 210 BC).
Along with many other things Shi Huang standardized the coinage system of the Chinese Empire. As new national currency he introduced round coins with a square hole in the middle. The new currency was known under the name "ban liang" (= half liang).