Khai Thai was the second reign title of Emperor Tran Minh Tong (1314-1329), after the reign title Dai Khanh. Minh Tong was a good King but had no vision. The Emperor did not realized Tran Khac Chung's plot and killed General Tran Khac Chan who was the Queen's father and was accused of plotting a coup. Later Emperor was told of his mistake. After 16 years on the throne, he turned the throne over to Tran Hien Tong and took the title of Highest King. In the 11th month of the last year of Dai Khanh, 1323, Emperor ordered to cast zinc coin. This was the first historical record about zinc coin in ancient Viet Nam. But only after one year, 1324, in the 12th month of the first year of Khai Thai, Tran banned zinc coins without explanation. Until now there was no Tran's zinc coin found in Viet land. Khai Thai nguyen bao coins were in copper, 25 mm and 3.8 gram.