Coin history - The Qin dynasty B.C. 221-207

In 221 B.C. in the 26th year of his reign, the King Shi eliminated the other six states, unified the country for the first time, and proclaimed himself the yellow emperor, Shi Huang Di. He was a hardworking and visionary ruler, but his regime was totalitarian. It was based on the thoughts of legalism which foundation was that man was basically evil, but could be controlled to be good. The hereditary aristocracy was abolished and the country was divided into 36 commanderies. All civil and military leaders were now appointed by merit. The new society was controlled in every way: weapons were confiscated, people relocated, books burned, and the written script, units and measures were standardized as was the coinage. The totalitarian order of the Qin dynasty was clearly a reaction against the chaos of the Warring States period, but the extreme taxes, laws and other burdens it placed on people became its fate, and the dynasty lasted only 14 years.

Both gold and bronze coins were used during the Qin. Gold was used for large money transactions, and one Jin of gold (see weights) was equal to 10.000 Ban Liang (Peng p. 102). The Ban Liang had been cast before the unification. Now it was made the new coin standard, and all the variations of the Warring States period were abolished. The ideal weight of the Ban Liang was equal to its denomination. One liang during the Qin was equivalent to approximately 17 grams. This means that the ideal Ban Liang should weigh approximately 8.5 grams. However, Peng (p. 78) writes that there were actually a variation in the Ban Liangs. The Ban Liangs he experimented with weighed between 6 and 20 grams. Enormous expenses to many large projects, caused the government to gradually lower the weight of the Ban Liangs during the period. 
Peng explains that many of the weapons which were confiscated in great numbers and also the coins from before the unification were recast into Ban Liangs. There were also many coins cast from virgin copper, so the standard of the metal was very uneven. The characters of the Ban Liangs were a high raised relief without a rim to protect it. Peng writes that this caused them to wear out quickly (p. 79). It is widely believed that it was the Qin emperor who created the coin type with square holes, and even Peng thought that (p. 79). There were, however, already several types of coins with square holes during the Warring States period. (See round coinage of the Zhou)