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708–958

Kōchō Jūnisen: The Twelve Ancient Court Coin Types

Kōchō Jūnisen is the conventional collective name for twelve official court coin types beginning with Wadō Kaichin in 708 and ending with Kengen Taihō in 958. The group is a chronological and historical framework, not evidence that every issue circulated equally, retained the same quality, or enjoyed the same public acceptance.

皇朝十二銭Kōchō Jūnisen

A Tokyo National Museum group illustrating the twelve ancient court coin types
Representative museum group; early-money objects are documented separately.National Institutes for Cultural Heritage, Japan / ColBase · CC BY 4.0
Date span
708–958
Issues
12
First
Wadō Kaichin
Final
Kengen Taihō

Sequence explorer

Twelve official court coin types

Literally 'the twelve coins of the imperial court.' Modern museum treatment groups Wado Kaichin with the eleven later court issues while separately recognizing earlier Fuhonsen.

  1. 01 和同開珎 Wadō Kaichin 708 · 和銅 1 Empress Genmei
    Weight
    3.4 g mean
    Diameter
    24.46 mm mean
    Mature page →
  2. 02 萬年通寶 Mannen Tsūhō 760 · 天平宝字 4 Emperor Junnin
    Weight
    2.56–6.69 g
    Diameter
    24.56–27.45 mm
    Mature page →
  3. 03 神功開寶 Jingū Kaihō 765 · 天平神護 1 Empress Shōtoku
    Weight
    2.5–5.6 g
    Diameter
    24.5–27 mm
    Register record
  4. 04 隆平永寶 Ryūhei Eihō 796 · 延暦 15 Emperor Kanmu
    Weight
    2.35–5.89 g
    Diameter
    24.03–27.88 mm
    Register record
  5. 05 富壽神寶 Fujū Shinpō 818 · 弘仁 9 Emperor Saga
    Weight
    2.13–4.59 g
    Diameter
    22.53–25.21 mm
    Register record
  6. 06 承和昌寶 Jōwa Shōhō 835 · 承和 2 Emperor Ninmyō
    Weight
    2.01–3.33 g
    Diameter
    20.47–23.36 mm
    Mature page →
  7. 07 長年大寶 Chōnen Taihō 848 · 嘉祥 1 Emperor Ninmyō
    Weight
    1.26–2.97 g
    Diameter
    19.24–21.21 mm
    Register record
  8. 08 饒益神寶 Nyōyaku Shinpō 859 · 貞観 1 Emperor Seiwa
    Weight
    1.47–2.98 g
    Diameter
    18.32–20.28 mm
    Register record
  9. 09 貞観永寶 Jōgan Eihō 870 · 貞観 12 Emperor Seiwa
    Weight
    1.74–3.4 g
    Diameter
    18.86–20.14 mm
    Register record
  10. 10 寛平大寶 Kanpyō Taihō 890 · 寛平 2 Emperor Uda
    Weight
    1.16–3.32 g
    Diameter
    18.04–20.25 mm
    Register record
  11. 11 延喜通寶 Engi Tsūhō 907 · 延喜 7 Emperor Daigo
    Weight
    1.85–3.64 g
    Diameter
    18.47–20.36 mm
    Register record
  12. 12 乾元大寶 Kengen Taihō 958 · 天徳 2 Emperor Murakami
    Weight
    2.83 g (1 observed specimen)
    Diameter
    19.96 mm (1 observed specimen)
    Mature page →

Comparative register

Identity, measurements, and evidence

Observed ranges include casting and condition variation. A single observation is not displayed as a range.

Seq.CoinInscriptionYear / eraAuthorityMetalWeightDiameterMajor noteConfidence
1Wadō Kaichin和同開珎708和銅 1Imperial court under Empress Genmeicopper alloy, silver issue3.4 g mean24.46 mm meanIssued in 708 as a state coin modeled within the Tang Kaiyuan Tongbao monetary and visual tradition. The court promoted use through rank incentives and payments connected with state construction.high for identity, issue date, inscription, and sequence; variable at specimen and subtype level
2Mannen Tsūhō萬年通寶760天平宝字 4Imperial court under Emperor Junnincopper alloy2.56–6.69 g24.56–27.45 mmIssued with the gold Kaiki Shōhō and silver Taihei Genpō. It was declared equal to ten Wado Kaichin, a policy that did not secure durable acceptance and encouraged private casting.high for identity, sequence, issue date, and authority; medium for generalized specifications
3Jingū Kaihō神功開寶765天平神護 1Imperial court under Empress Shōtokucopper alloy2.5–5.6 g24.5–27 mmThe third issue in the official twelve-coin sequence, released during Empress Shōtoku's reign after the 760 replacement coinage.high for identity, issue date, authority, and sequence; medium for generalized measurements
4Ryūhei Eihō隆平永寶796延暦 15Imperial court under Emperor Kanmucopper alloy2.35–5.89 g24.03–27.88 mmDeclared at ten old coins per new coin. Older coin use was initially restricted, then permitted again in 808 when the supply of new coin was insufficient.high for identity, issue date, authority, and policy context
5Fujū Shinpō富壽神寶818弘仁 9Imperial court under Emperor Sagacopper alloy2.13–4.59 g22.53–25.21 mmOfficial records addressed production targets and accepted poorly formed or partly illegible pieces, illustrating supply pressure and declining production quality.high for identity, issue date, authority, and historical quality evidence
6Jōwa Shōhō承和昌寶835承和 2Imperial court under Emperor Ninmyōcopper alloy2.01–3.33 g20.47–23.36 mmIssued in Jōwa 2 and identified by the Currency Museum as the first Japanese coin whose inscription used the era name.high for identity, issue date, authority, and era-name significance
7Chōnen Taihō長年大寶848嘉祥 1Imperial court under Emperor Ninmyōcopper alloy1.26–2.97 g19.24–21.21 mmIssued after the appearance of a white turtle and the era change to Kashō; the name expresses longevity.high for identity, issue date, authority, and documentary context
8Nyōyaku Shinpō饒益神寶859貞観 1Imperial court under Emperor Seiwacopper alloy1.47–2.98 g18.32–20.28 mmIts name expresses abundant benefit or wealth. Currency Museum commentary treats it as particularly scarce among the Heian issues, but this catalog does not convert that observation into a census.high for identity, issue date, and authority; medium for comparative rarity wording
9Jōgan Eihō貞観永寶870貞観 12Imperial court under Emperor Seiwacopper alloy1.74–3.4 g18.86–20.14 mmThe court opened a new office, recalled old coins, and in 872 criticized poor lettering and weak rims after market rejection. This is direct evidence that quality and trust were linked.high for identity, issue date, authority, and documented quality complaint
10Kanpyō Taihō寛平大寶890寛平 2Imperial court under Emperor Udacopper alloy1.16–3.32 g18.04–20.25 mmBy this issue, new coinage was no longer closely tied to major capital-construction payments in the way early state coin use had been.high for identity, issue date, authority, and sequence
11Engi Tsūhō延喜通寶907延喜 7Imperial court under Emperor Daigocopper alloy1.85–3.64 g18.47–20.36 mmThe Engi-shiki permitted use of a coin if one character remained clear, evidence of how far legibility and manufacturing quality had declined.high for identity, issue date, authority, and documentary quality rule
12Kengen Taihō乾元大寶958天徳 2Imperial court under Emperor Murakamicopper alloy2.83 g (1 observed specimen)19.96 mm (1 observed specimen)Issued in 958, Kengen Taiho was the final new issue in the official ancient court sequence. Domestic coin issuance then ceased for centuries while commodity money and, later, imported Chinese cash filled monetary roles.high for identity, issue date, authority, and final-sequence position; low for generalized measurements because only one catalog specimen was measurable

Measured trend

Observed diameter and weight shift

Bar length uses each issue's range midpoint or catalog mean. It visualizes the source data; it does not fill gaps or define official standards.

DiameterWeight
1Wadō Kaichin
24.46 mm
3.40 g
2Mannen Tsūhō
26.00 mm
4.63 g
3Jingū Kaihō
25.75 mm
4.05 g
4Ryūhei Eihō
25.95 mm
4.12 g
5Fujū Shinpō
23.87 mm
3.36 g
6Jōwa Shōhō
21.91 mm
2.67 g
7Chōnen Taihō
20.23 mm
2.12 g
8Nyōyaku Shinpō
19.30 mm
2.23 g
9Jōgan Eihō
19.50 mm
2.57 g
10Kanpyō Taihō
19.14 mm
2.24 g
11Engi Tsūhō
19.41 mm
2.75 g
12Kengen Taihō
19.96 mm
2.83 g

Repeated monetary interventions

New issues repeatedly attempted to restore supply, revenue, and the court's preferred unit of account. Declaring a new coin equal to ten old coins could create nominal value without guaranteeing acceptance.

Metal, size, and manufacture

Museum measurements show a broad shift from larger early pieces toward smaller later ones. Chemical samples show changing copper, tin, lead, iron, arsenic, and antimony patterns. These are trends across measured specimens, not one fixed formula for each name.

Quality and trust

Copper scarcity, more lead, weak rims, poor lettering, private casting, high official exchange ratios, and inadequate supply interacted. The decline was institutional and material, not a single-cause story.

After 958

After Kengen Taiho, the court issued no new coin type for centuries. Rice, silk, and cloth served monetary roles before large imports of Chinese cash later reshaped circulation.

Evidence

Sources and scope

These links support the claims on this page. Source authority does not imply permission to republish source images.

History of Japanese Currency Currency Museum, Bank of Japan

Fuhonsen and Mumon Ginsen context, the 708 issue of Wado Kaichin, state monetary policy, quality decline, the 958 final issue, and the return to commodity money.

Open source
Ancient Coins: Wado Kaichin and the Later Eleven Issues Currency Museum, Bank of Japan

Official museum grouping, specimen catalog, readings, and specimen-level measurements for the twelve court coin types.

Open source
Currency Museum Learning Sheet Answer Booklet Currency Museum, Bank of Japan

The canonical order and issue years of the twelve ancient court coin types.

Open source
Wado Kaichin and Ancient Coinage Exhibition Catalogue, Pages 1–5 Currency Museum, Bank of Japan

Mumon Ginsen, Fuhonsen, Wado Kaichin, Mannen Tsuho, Jingu Kaiho, documentary issue dates, circulation policy, and reading evidence.

Open source
Wado Kaichin and Ancient Coinage Exhibition Catalogue, Pages 11–15 Currency Museum, Bank of Japan

Issue dates, emperors, policy evidence, production decline, and historical notes for Ryuhei Eiho through Kengen Taiho.

Open source
Chemical Composition Study of the Twelve Ancient Coin Types Institute for Monetary and Economic Studies, Bank of Japan

Measured copper, tin, lead, iron, arsenic, and antimony patterns across sampled ancient coins, with specimen-level limitations.

Open source