Kocho Junisen

kōchō jūnisen (皇朝十二銭) (aka jūnizeni) is a general term for 12 types of copper coins minted in Japan under the Ritsuryo system from 708 (Wadō 1st year) to 963 (Ōwa 3rd year).^[1] All of the included coins are circular in shape, have a square hole in the center, and were worth 1 mon.^[a]

History

Japan's first formal currency system was the Kōchōsen (Japanese: 皇朝銭, "Imperial currency"). It was exemplified by the adoption of Japan's first official coin type, the Wadōkaichin.^[2]^[3] It was first minted in 708 CE on order of Empress Genmei, Japan's 43rd Imperial ruler.^[2] "Wadōkaichin" is the reading of the four characters printed on the coin, and is thought to be composed of the era name Wadō (和銅, "Japanese copper"), which could alternatively mean "happiness", and "Kaichin", thought to be related to "Currency".

The Kōchōsen Japanese system of coinage became strongly debased, with its metallic content and value decreasing. By the middle of the 9th century, the value of a coin in rice had fallen to 1/150th of its value of the early 8th century.^[4] By the end of the 10th century, compounded with weaknesses in the political system, this led to the abandonment of the national currency, with the return to rice as a currency medium. The last official Japanese coin emission occurred in 958, with very low quality coins called Kengen Taihō (乾元大宝), which soon fell into disuse.^[4]

Coins

Inscription	Kyūjitai	Shinjitai	Year of introduction (Julian calendar)
Wadōkaichin	和同開珎	和同開珎	708
Mannen Tsūhō	萬年通寳	万年通宝	760
Jingū Kaihō [ja]	神功開寳	神功開宝	765
Ryūhei Eihō [ja]	隆平永寳	隆平永宝	796
Fuju Shinpō [ja]	富壽神寳	富寿神宝	818
Jōwa Shōhō [ja]	承和昌寳	承和昌宝	835
Chōnen Taihō [ja]	長年大寳	長年大宝	848
Jōeki Shinpō [ja]	饒益神寳	饒益神宝	859
Jōgan Eihō [ja]	貞觀永寳	貞観永宝	870
Kanpyō Taihō [ja]	寛平大寳	寛平大宝	890
Engi Tsūhō [ja]	延喜通寳	延喜通宝	907
Kengen Taihō [ja]	乹元大寳	乾元大宝	958