The Kaiyuan Tongbao (), sometimes romanised as Kai Yuan Tong Bao or using the archaic Wade-Giles spelling K'ai Yuan T'ung Pao,Sportstune.com K'ai Yuan coins by John Ferguson. Retrieved: 21 June 2018. was a Tang dynasty cash coin that was produced from 621 under the reign of Emperor Gaozu and remained in production for most of the Tang dynasty until 907. The Kaiyuan Tongbao was notably the first cash coin to use the inscription tōng bǎo (通寶) and an era title as opposed to have an inscription based on the weight of the coin as was the case with Ban Liang, Wu Zhu and many other earlier types of Chinese cash coins. The Kaiyuan Tongbao's calligraphy and inscription inspired subsequent Central Asian, Japanese, Korean, Ryūkyūan, and Vietnamese cash coins and became the standard until the last cash coin to use the inscription "通寶" was cast until the early 1940s in French Indochina.
The Kaiyuan Tongbao also signified a major change in how money circulated in the Chinese Empire, while previously cash coins were valued based on their weights, they would now be valued based on government regulations.
After the fall of the Tang dynasty Kaiyuan Tongbao coins would continue to be produced by various states of the Five Dynasties and Ten Kingdoms period.
During the Ming dynasty, and later dynasties, the Kaiyuan Tongbao would become the most important cash coin to be used in traditional Chinese medicine.古文錢，但得五百年之外者即可用，而唐高祖所鑄開元通寶，得輕重大小之中，尤為古今所重 (Ancient money can be used if it is more than five hundred years old, but the Kaiyuan Tongbao cast by Emperor Gaozu of the Tang Dynasty is especially important in ancient and current times.) - Compendium of Materia Medica（明·本草綱目）by Li Shizhen (李時珍).清朝的《本草拾遺》也提到“唐開元錢燒之有水銀出”。(in Classical Chinese).
Manufacture
Wax mother coins
Under the Sui and Tang dynasties mother coins reached their definite form and were produced in moulds engraved by ancestor coins, however during this same period a casting technique called "the lost wax method" was used to cast the Kaiyuan Tongbao cash coins, in this method mother coins made from wax rather than metal were used, these mother coins were produced in large quantities because they were very cheap to make, unlike metal mother coins these wax mother coins stayed in the clay moulds and when the mould heated up they would melt away leaving a cavity for the molten metal to pour into forming the coins. This technique was also used for casting other bronze items however it was only used for casting coinage during the Sui and Tang dynasties and its sudden discontinuation pointed out to the fact that it was probably inefficient for mass-producing small items such as coins.Ancient Chinese Coins - "The casting of coins during the Tang " by Lars Bo Christensen. Retrieved: 09 July 2018.
Clay moulds
Various moulds were used in coin casting. See the Chinese Wikipedia page on 錢範.
The world's only known authentic specimen of a Tang dynasty period clay mould () that was used to cast Kaiyuan Tongbao cash coins was unearthed in Shutang, Wangcheng District, Changsha, Hunan on August 17, 1992, by Mr. Ceng Jingyi (), a retired teacher and coin collector. The Kaiyuan Tongbao clay mould is classified as a Chinese "national treasure" ().
Up until the unearthing of this clay mould in the year 1992, no moulds were known to exist for the casting of Tang dynasty coinage. The discovery of this clay mould has made it unclear as to what process was actually used to cast the Kaiyuan Tongbao cash coins.
While the Kaiyuan Tongbao cash coins could have been cast in the traditional manner from moulds made of clay, stone, or bronze as was the case since the Warring States period, it was believed that cash coins during this period were being cast in sand using "mother coins" (母錢) to make the impressions where the circulation cash coins would later be produced from. With the discovery of this unique clay mould, however, it has now been confirmed that clay moulds were still being used by mints to cast cash coins during the Tang dynasty period.
The unique Kaiyuan Tongbao clay mould was placed on display at the "Exhibition of Chinese Ancient Coins" () which was held at the Ouyang Xun Cultural Park () located in Shutang ().
History
Under the Tang dynasty the earlier Wu Zhu coins of the Sui dynasty would remain the standard currency, but during the fourth year of the Wu De (武德) period (or 621 of the Gregorian calendar) Emperor Gaozu decreed that the Kaiyuan Tongbao coin be cast with a strictly enforced standard weight of Liǎng (兩).Li Xueqin (李學勤), Lü Wenyu (呂文鬰) (1996). Siku da cidian (四庫大辭典), vol. 2, p. 1859. Changchun: Jilin daxue chubanshe. (in Mandarin Chinese).Wang Yi (王益), Bai Qinxian (白欽先) (ed. 2000). Dangdai jiinrong cidian (當代金融辭典), Beijing: Zhongguo jingji chubanshe, p. 808. (in Mandarin Chinese) The introduction of this new series of cash coins proved to be of epochal significance in the monetary history of China as the new coin started the "Baowen coinage" system (together with the Ban Liang cash coins introduced during the Qin period and Wu Zhu cash coins introduced during the Han period, making them the three major coinage systems in monetary history of China), which influenced the Chinese coinage system for over a millennium. The Kaiyuan Tongbao also changed the way that cash coins were valued, as before they were dependent on their weight but starting from the Kaiyuan Tongbao the value of a cash coin would be determined by government regulation. The government of the Tang dynasty initially set up the Money Casting Bureau, which operated mints in a total of 14 locations.
Unlike earlier Chinese cash coins which had their legends based on their weight, the Kaiyuan Tongbao was notably the first Chinese cash coin to use the tōng bǎo (通寶) inscription and simultaneously inspired the yuán bǎo (元寶) inscription. The reason that the Kaiyuan Tongbao also inspired the yuán bǎo legend is because the Chinese people themselves had trouble figuring out the correct character order, as the inscription is read in what was referred to as the "standard order" (top-bottom-right-left) some people accidentally read it in the wrong order as they had assumed that the inscription was read clockwise as Kaitong Yuanbao (開通元寶), this was also because rather than having the first two characters spell out the period title (which was Wu De when the Kaiyuan Tongbao was introduced), they had a different inscription. However this mistake in how the legend was read inspired the Northwest Chinese rebel Shi Siming to cast his own cash coins with the inscription Shuntian Yuanbao (順天元寶, shùn tiān yuán bǎo) cash coins first issued in Luoyang in 759, this coin however does have a clockwise inscription. Another term that was used to denote "the currency type" in Chinese coin inscriptions was zhòng bǎo (重寶) which could be translated as "heavy currency". The first cash coin to have this inscription was the Qianyuan Zhongbao (乾元重寶) which was first produced in the year 759. The terms yuán bǎo (元寶) and zhòng bǎo (重寶) which were both established during a 138-year period of the Tang dynasty would continue to be used on Chinese coins to the very end of the Qing dynasty in 1911.Anything Anywhere. CHINA, coins of the Tang dynasty, 618-907 AD by Bob Reis. Retrieved: 09 June 2018.Calgary Coin & Antique Gallery - MEDIEVAL CHINESE COINS - THE SUI, T'ANG AND POST TANG DYNASTIES by Robert Kokotailo. Retrieved: 09 June 2018.Numis' Numismatic Encyclopedia. A reference list of 5000 years of Chinese coinage. (Numista) Written on December 9, 2012 • Last edit: June 13, 2013 Retrieved: 09 June 2018. While the term tōng bǎo (通寶) was even used longer with the last Chinese cash coin, the Minguo Tongbao (民國通寶) being produced in Dongchuan, Yunnan during the early Republic of China period.
Another important difference with the inscription of the Kaiyuan Tongbao compared to earlier Chinese cash coins was that it was not written in seal script but rather in the more plain calligraphic clerical script. The Emperor asked one of China's most well-known calligraphers, Ouyang Xun to write down the legend of the cash coin. This was also the first time in Chinese history that a famous calligrapher wrote the characters for a Chinese cash coin. Minting and copper extraction were centrally controlled, and private casting was punishable by death. For the first time we find regulations giving the prescribed coinage alloy: 83% copper, 15% lead, and 2% tin. Previously the percentages used seem to have been on an ad hoc basis. Actual analyses show rather less copper than this.
The standard weight of the Kaiyuan Tongbao was 1 mace, but a notable thing about the cash coins of the Tang dynasty is, that for the first and only time in the monetary history of China, the coins grew bigger and heavier during the reign of the dynasty.Jen, David: Chinese Cash, Identification and Price Guide. - Krause Publications, US. 2000. Page: 39.
The New Book of Tang states that the imperial government specified the alloy ratio for Kaiyuan Tongbao cash coins upon their introduction at 21,200 jin of copper, 3700 jin of pewter, and 500 jin of black tin (equivalent to 83% Cu and 17% Pb + Sn) per mint. At first, mints were set up in Luoyang in Henan, and also in Peking, Chengdu, Bingzhou (Taiyuan in Shanxi), and then Guilin in Guangxi. Minting rights were also granted to some princes and officials. By 660, deterioration of the coinage due to forgery had become a problem. The regulations were reaffirmed in 718, and forgeries suppressed. In 737, the first commissioner with overall responsibility for casting was appointed. 1 furnace that produced 3.3 million Kaiyuan Tongbao coins a year during the Tian Bao period between 713 and 756 would need 21220 jin of copper, 3709 jin of tin, and 540 jin per regulation of lead and had an average waste of 23,5 %. The Kaiyuan Tongbao cash coins produced during the Tian Bao period had an officially set copper alloy however some Kaiyuan coins from this period were blue or white it's likely that other alloys were also used.Ancient Chinese Coins - The casting of coins during the Tang by Lars Bo Christensen. Retrieved: 09 July 2018.Peng, Xinwei: A Monetary History of China. vol I. and II. (Translated from the Chinese original Zhongguo Huobi Shi 1965 by Kaplan, Edward H.) 1994 Western Washington University. In 739, ten mints were recorded, with a total of 89 furnaces casting some 327,000 strings of cash a year. 123 liang of metal were needed to produce a string of coins weighing 100 liang. In the late 740s, skilled artisans were employed for casting, rather than conscripted peasants. Despite these measures, the coinage continued to deteriorate. In 808, a ban on hoarding coins was proclaimed. This was repeated in 817. Regardless of the rank of a person, they could not hold more than 5,000 strings of cash. Cash balances exceeding this amount had to be expended within two months to purchase goods. This was an attempt to compensate for the lack of cash in circulation. By 834, mint output had fallen to 100,000 strings a year, mainly due to the shortage of copper. Forgeries using lead and tin alloys were produced.
Due to the fact that this continued to be produced for two centuries by various mints all over China there are several hundred varieties of the Kaiyuan Tongbao that can be distinguished from each other due to slight differences.