The currency of the Qin dynasty. Copper casting, square hole, the diameter of money is generally 2.5-2.77 cm, weighing 12 baht (24 baht in ancient China was 1), 2.5-3.35 grams, and some have foreign fruits, which are plain, and the word "half two" is written on the surface. In 22 1 year BC, Qin unified the world, stipulating that the excircle was the national currency, which was the earliest unified currency in China.

The circulation scope of Qin Banliang money extends westward to Hexi Corridor; East to Shandong and Jiangsu, north to Inner Mongolia, south to Guangzhou, northeast to Liaodong Peninsula and southwest to the upper reaches of Dadu River, indicating that Qin Banliang is the national currency.

The "Qin Banliang" copper coin takes a "square hole" as the coin shape, the square hole represents the place, and the excircle represents the round sky. The "round hole" symbolizes the world view of the ancient round sky (this is a generally accepted view.

However, some people think that the circular square hole is the need of production and processing, the need of portability, circulation and storage, and a more scientific system formed in continuous practice.

The word "half Liang" on the copper coin is a small seal script, which was inscribed by the famous Qin Li Si. It means that each piece weighed half two (that is, twelve baht) at that time, so it was called "half two".

Historical Records quoted by the historian Ping Zhun notes ancient and modern times: Qin Qian was half a tael, with a diameter of one inch and two cents and a weight of twelve baht. Today, Qin Banliang's money varies in size, with a diameter of 3.2-3.4 cm and a weight of about 8 grams. Qian Wen is long and narrow, slightly curved. No inner and outer Guo, flat back. Some of them weigh more than10g, even more than 20g, or they are Dangbaiqian contained in Suoyin.