Kaiyuan (7 13 years1February -74 1 year1February) is the year number of Xuanzong of the Tang Dynasty, which is 29 years. Kaiyuan means opening a new era. During the Kaiyuan period, the national strength of the Tang Dynasty was strong, which was known as the prosperity of Kaiyuan in history.
The Tang Dynasty coin Kaiyuan Bao Tong was issued by Tang Gaozu Li Yuan. Never think that it was promulgated by Emperor Xuanzong of the Tang Dynasty. This is a major monetary reform, ending the five-coin era since the Han Dynasty.