During the Warring States Period of China, there were round coins with square holes in the currency of Qi, Yan and Qin. The coins of Qi State have inner and outer Guos on the front and flat backs on the back. They are divided into three types: large, medium and small. The largest one is "Liu Hua", or "six knives", with a diameter of about 3.4 cm and a weight of about 8 grams. Followed by "Sihua", the diameter is about 3 cm and the weight is about 5 grams. The smallest is "hua", with a diameter of about 2 cm and a weight of 1.1 to 2 grams. The text belongs to the Warring States period.
In 210 BC, Qin Shi Huang abandoned the currency of different shapes in the whole country, and uniformly made currency in the shape of a round square hole.
In the next 2000 years, the round square hole money was kept and adopted by every emperor as the main currency form until the end of the last round square hole money in the Republic of China. the stage of Chinese currency.
