± 731

The Kai Yuan Tong Bao has been minted since 621. This coin was the first edition of the Tang dynasty (618-907) as cash. The name means "circulating treasure of the inauguration of a new age". Like many other Chinese coins, the value was determined by weight. The calligraphy and inscription of this coin inspired later Central Asian, Korean, Japanese, Vietnamese and Ryukyuan coins and became the standard until the last cash coin to use the inscription until the early 1940s. Under the Sui and Tang Dynasties, mother coins reached their final form. Mother coins were produced in molds engraved by ancestor coins. During the same period, the “lost wax method” casting technique was used to cast Kai Yuan Tong Bao money coins. These were cheap to manufacture and were made in enormous quantities.

The older Wu Zhu coins of the Sui Dynasty remained the default currency. In 621, Emperor Gaozu ordered that the Kai Yuan Tong Bao coin be cast with a standard weight of 1/10 Liang (= 50 gr.). The Chinese people themselves had trouble reading the inscription according to the standard order of top-bottom-right-left. Some people read it in the wrong order assuming that the inscription was read clockwise and thus took on new meaning. Another significant difference with the inscription was that it was not written in seal script, but with more simple calligraphic clerical script.

The beating was centrally controlled. Private casting was punishable by death. By 660, the deterioration of the coins due to counterfeiting had become a problem. Forgeries were suppressed in 718 as the precepts were reaffirmed. The first commissioner with overall responsibility for casting was appointed in 737. In the late 740s, craftsmen were employed for casting, rather than conscript farmers. To prevent the hoarding of coins, the holding of cash was restricted in 817. Coins were produced all over China for two centuries, leaving many variants in circulation.