Kaiyuan Tongbao was the currency of Tang Dynasty, and coins had Tongbao since Tang Dynasty. At the beginning of Tang Dynasty, the Sui and five baht were used, which was light and confusing.
In the fourth year of Wude (621) of Gaozu in Tang Dynasty, in order to rectify the disordered currency system, sui qian was abolished and the strict norms of the five Bahts in the Western Han Dynasty were followed.
Kaiyuan Tongbao was cast to replace the five Bahts left in the society. There are five coins in total, which are the treasure of Mr. Lu's family.
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