As long as there is demand, there will be a market. As long as there is a market, organizations and individuals serving transactions will naturally emerge. This is an interest system. Whether from top to bottom or from bottom to top.

My own opinion is that it was not possible to set up currency exchange institutions between countries at that time. At that time, China was only in the early stage of the development of feudal society and its productivity was low. The internal motivation of national transactions is not enough to promote the emergence of national exchange institutions.

It is possible that, just like the circulation of RMB in Southeast Asian countries near the border of China in previous years, there are specialized people and non-governmental organizations there to exchange RMB. Of course, they are profitable (in ancient times, they should charge fees, but now they mainly earn the difference with the official exchange rate. ）； When regional trade reaches a certain level, it will give birth to official exchange institutions. Of course, private exchange rate and official exchange rate can coexist.

finally, I want to exchange knife coins and cloth coins in business, which should be convertible both at home and abroad. I hope I can explain clearly!