There is a closed mountain village, the main work of the villagers is to dig jade, the wealth of the village is also calculated in jade. We dig jade stacked together, by the village head count accounting. The wealth of Zhang SAN, Li Si and Wang Wu was recorded in the village chief's account book, and they could exchange it for other daily necessities. This approach is now known as the central book-keeping financial system. Banks, brokerages, Alipay and other financial institutions are vi...