"Bao Tong" means precious commodities, and "Bao Tong" is the name of ancient Chinese coins. It originated from Kaiyuan Bao Tong, which was cast by Tang Gaozu Wude for four years. It has been used throughout the ages. The word "Bao Tong" usually begins with the year number, dynasty or country name and is cast on the surface of coins. For example, Bao Tong in the Tang Dynasty in the Southern Tang Dynasty, Taiping Bao Tong in the Song Dynasty, Justice Bao Tong in the Yuan Dynasty, Daming Bao Tong in the Ming Dynasty and Kangxi Bao Tong in the Qing Dynasty.
Since Hongwu, there have been castings in Yongle, Xuande, Hongzhi, Jiajing, Qin Long, Wanli, Taichang, Apocalypse and Chongzhen. By the end of the Ming Dynasty, the governors called themselves emperors and kings, acting independently and making money by themselves, showing a scene of enduring prosperity. Zhu Yihai, the king of Lu, cast Daming in Jiangsu and Zhejiang, Zhu Yousong, the emperor, in Nanjing, Zhu Zhulong, the emperor, in Fuzhou, and Zhu Youlang, the emperor, in Zhaoqing, cast Bao Tong. Li Zicheng voted for Yongchang when Ann proclaimed himself emperor, and Zhang voted for Dashun when he proclaimed himself emperor in Chengdu.
So what is the value of commodities in the Ming Dynasty? According to Wan Shu Zatan in Wanli period of Ming Dynasty, Shi Ming and Scholars in Kangxi period of Qing Dynasty, we can calculate one yuan a day. January 3 Liang, rice silver 1 Liang =2 stone, which is 377.6 Jin. Rmb 1.75/ kg, equivalent to RMB 660.8, so one dollar is equivalent to RMB 66 yuan.
When different emperors came to power, all legal commodities were Bao Tong with the title of contemporary emperor. Different emperors used this Bao Tong to control the economy. Obviously, Chao Tongbao should change the dynasty, but among the people, Bao Tong, who had the title of emperor at that time, could be exchanged according to the fineness of copper coins.