Kocho-Junisen (twelve coins cast in Japan) (皇朝十二銭)

"Kocho-Junisen" is a collective term for twelve kinds of copper coins cast in Japan during the period from 708 AD to 963 AD. They are also called "Honcho-Junisen" and "Kocho-Junimonsen."

Its Issue and History
Kocho-Junisen includes the following twelve kinds of coins.

Wado-kaichin, in 708. Mannen-tsuho, in 760. Jingu-kaiho, in 765. Ryuhei-eiho, in 796. Fuju-shinpo, in 818. Jowa-shoho, in 835. Chonen-taiho, in 848. Nyoeki-shinpo, in 859. Jogan-eiho, in 870. Kanpyo-taiho, in 890. Engi-tsuho, in 907. Kengen-taiho, in 958.

Each coin of the above has a square hole in the circular form.
They circulated as currency of one mon each (an old currency unit in Japan) as ordained by the ritsuryo government (ancient Japanese government of centralized governance.)
Beside the above, gold coins named Kaiki-shoho and silver coins named Taihei-genpo were cast on a trial basis in 760 AD, but they failed to circulate as widely as the copper coins.

Kocho-Junisen are considered to have been issued for the purpose of setting Japan's currency system in order by modeling the example of the Kaigen-tsuho of the Tang dynasty of China and also for the purpose of raising funds to cover huge costs required for transferring the national capital to Heijo with margins of profit from the value of currency and the original value of copper material.

Wado-kaichin is the oldest one among the currencies evidently believed to have in fact circulated in Japan. Fuhonsen coins which appear to be older than Wado-kaichin are not distinctly defined yet to have in fact existed. In 711, three years after issue of Wado-kaichin, Chikusen-joirei (an ordinance to ordain a court rank to someone who saved a certain amount of money) was issued. Although paradoxical it is, this ordinance of chikusen-shorei (encouragement to save money) is considered to have been issued in order to promote circulation of the currency. However, no real execution of such an order has been reported except the case implemented in November of the same year of the ordinance.
At that time in Japan, rice and cloth were the popular items to exchange as material money, because then-current society of Japan had not reached yet to the economic level to necessiate money currencies, and therefore circulation of money was limited to the Kinai area (countries near Kyoto.)
Also, even if there had been enough demand, the volume of copper production had been absolutely small, which made it impossible, from the beginning, to supply sufficient copper coins and substitute material money then-current in Japan (copper was so precious then in Japan that its era was renamed 'Wado (literally, Japanese copper),' upon discovery of copper ore mines, and, as described afterward, the quality of copper coins had rapidly deteriorated as time went on.)
And, locations of the copper mines had spreaded everywhere in Japan, from Hokkaido to Kumamoto Prefecture.

Only after 52 years from issue, Wado-kaichin was renewed into Mannen-tsuho coins. Then, the value of one new Mannen-tsuho coin was decided to be equivalent to ten coins of the old Wado-kaichin. A similar decision was made, repeatedly, in the subsequent coin renewals. Every time the coins were renewed, Kocho-Junisen (twelve coins cast in Japan) decreased in size and weight and materials became worse. One of reasons for the above was that usable materials by the then-current technology of copper refinery, was limited to certain resources, so that production of such usable copper resources continued to decrease year by year. In the beginning of Wado-Kaichin era, people could buy 2kg of rice at one mon each, but in the middle of ninth century the available quantity of rice for one mon decreased drastically to a one-hundredth or two-hundredth. Many coins of Engi-tsuho and the last Kangen-taiho contained so much lead that they were called lead coins instead of copper ones. Degraded coins became gradually avoided in the market of distribution and trading of commodities, and thus circulation of the coins inside Japan became limited in quantity before the latter half of 12th century when a lot of Sung dynasty currency from China entered Japan.

Hasen-undo (movement to melt coins to use as raw materials)
Then-current coins were small in unit value and used mostly in bundles as they had square holes in the center and were called holed coins. Therefore, they were so inconvenient to use because they had to be unbundled each time to identify official marks, a very necessary process to eliminate any false money or devalued currency from the Tang and Sung dynasty and that had a tendency to invite inflation.
Such acts of using false money or devalued currency were called 'degradation of money.'
Then government had ordered its ichi-no-tsukasa (governmental organization) to regulate prices of commodities for fixing at high the value of currency, but as a result, such initiation of the government helped to increase fraudulent acts of money-exchange by using cheap coins made and used in China. This tendency was accelerated by lowering the dignity of the coins. It was not difficult to alter such large-size Chinese coins as Wadosen (Japanese copper coins) into thin and small-size coins to be used in Japan.

A further problem was caused by redenomination of each new currency into one thousandth. From the beginning, the government's way to decide a new denomination was problematic, because, for example, it made a groundless decision to fix the new money's value at 10 times the old, citizens were forced to suffer devaluation of their savings of old money to one tenth their original value. That is why people refused exchanging old money, and rather preferred to melt them down into copper products. Suppose, for example, 10 coins of the old ten-yen currency could be changed into 1 new ten-yen coin, the value of the old ten-yen coin becomes only one tenth, which means melted copper ingots may have more value than the new copper coins. Even today, a similar problem may occur unless a newly issued ten-yen coin is acknowledged to have the equivalent of 100 yen value. Furthermore, as mentioned above, native copper ores used by then-current refining technology were limited to cuprate only and the abundant reserves of copper sulfide under the ground could not be used. All copper oxide mines located around Japan had drastic fear of the depletion of resources, which caused a raise in the value of copper. It is now understood that, no matter how the economy had developed at that time, people then carried out extensively the hasen (to melt coins to use as a raw material) so that at least a few thousand million pieces of issued coins could hardly be retrieved and the remaining coins were compelled to degraded values.

In response, the government officially announced in 984 the Kin-hasen Rei (an act banning the melting of coins to use as raw materials), making it extremely difficult to issue new money. This Kin-hasen Rei was promulgated toward shrines and temples, who used to melt copper coins to produce, for example, Buddhist alter articles such as hanging copper lanterns 'made to pray for national peace and security,' and therefore, to whom the Imperial Court could hardly complain against their illegal acts. As a result, number of existing Kocho-sen coins has become far fewer than recorded, with specifically inferior quality casting particularly in the latter period making them now corroded and difficult to read their engraved letters, while quite a few coins with readable letters are now priced high.

The End of the Kocho-sen Coins
Thus, copper coins issued by the government had lost the trust of the people and ceased to be used in the market. No copper coins followed after Kangen-taiho, partly due to weakening power and dignity of the Imperial Courts. Subsequently, there could be found no record concerning the then-used currencies in Japan since the beginning of 11th century, when the economy had returned back to the old material bartering system using rice, silk, and other commodities as a trading medium.
However, this does not mean that the demand for metal currencies vanished completely, after three hundred years or so for forming them in the Kinai area (countries near Kyoto,) but they remained as a method of conversion to decide official prices by Kokaho (acts of conversion rate of goods.)
Along with the development of economy in Japan, there appeared the use of new currencies imported from China, such as those of Yuan and Ming.

In Japan for a long time since abolishment of Kocho-Junisen (twelve coins cast in Japan,) no official currency was cast by the government. Resumption to use official copper currencies cast by the government happened more than 600 years after the period of Kocho-Junisen, when Keicho-tsuho and Kanei-tsuho appeared in the market in 1608 and in 1627, respectively.

Additional Remarks
Before Wado-kaichin coins, other currencies might have possibly been cast for use. One possibility is Mumon-ginsen coin (Japan's oldest private silver coinage) and another one is the Fuhon-sen coin.

Also used as quasi-money were Fuka coins (spade-shaped bronze coins.)
In China, holed coins had circulated in the market before Tosen coins (Chinese currency of the Tang dynasty) appeared, but, during the blank period without such currencies, it was cloth and rice that played the role as a bartering currency. One of the reminders of this fact is the term 'Chofu (literally, procurement of cloth),' which meant the national tax.
Copper, gold dust, silver, and others which were used as 'Shokudo (penalty charges)' may be regarded as a kind of Hyoryo kahei (currency valued by weight.)
Tettei (iron rod) of the Kofun period (tumulus period) may be regarded as equivalent to Kafu (ancient Chinese currency made of bronze,) used as Quasi-money, which is typically represented by Tosen currency (bronze coin shaped like an opened straight razor) of ancient China.

[Original Japanese]