In the 4th century BC the first coins were made by Chinese people, but those coins were different from modern ones. Those coins were shaped like a hatchet with a circle on the end. But they were uncomfortable to use, so they changed it leaving only the round part. In the middle of coins were quadrangle holes. The Chinese people thought that they situated in the middle of the universe. So, the round coin symbolized the world and the square was the border of China.
The hole was used in order to wear coins on belts. At that time, people did not have "change". They just gave each other bunches of coins according to a proximate weight. We can learn from ancient coins who the leader of the country was, where and when they lived. Each coin had the name of a leader written on it, and the year when the coin was made. Some coins from Kyrgyzstan even had more than 33 words written on them. The proximate price for one horse was 21 000 coins. Basically, any coin was priced at a value of a piece of metal which it was made of. There were three different kinds of coins - gold, silver and bronze. They were named denar, dirhem and fun, respectively. If somebody had enough metal to make some coins, he could do this without fear to be counterfeiter. For the same reason in circulation could be money of different countries and times.