Kyōhō Koban
享保小判（Kyōhō koban）
- Series
- Edo-period koban (1-ryō gold)
- Denomination
- 1 ryō
- Period
- Minting began 1715 (Shōtoku 5)
Updated: 2026-09-02
Specifications
| Item | Value | Type | Sources |
|---|---|---|---|
| Fineness & weight (catalog) | 87% / 18g / 1715年 | Catalog value | [1] |
| Prescribed fineness (kinza records) | 50.7勾位＝86.79% | Historical source | [2] |
| Meiji-era proclamation value | 86.70% | Historical source | [2] |
| Measured (XRF, specimens) | 85.7〜86.6% | Measured | [2] |
FACTThe Currency Museum catalog lists 87% fineness and 18 g (both rounded) with the year 1715.[1]
FACTThe kinza-document prescribed standard is 50.7勾位 = 86.79%; per cent = (44 / kurai) × 100.[2]
FACTThe Meiji-government series (Dajōkan Proclamation No. 93, 1874) lists 867.0‰ (86.70%). Documentary standards, measurements and Meiji proclamations are distinct series, deliberately not merged.[2]
MEASUREDNon-destructive analysis (electron-beam-excited X-ray, 3 specimens held by the Bank of Japan IMES) measured 85.7–86.6% gold and 17.70–17.75 g.[2]
Varieties & Attribution
MEASUREDSpecimens minted on Sado and classified as Kyōhō koban (Kyōhō ⟨Sado⟩) are distinguished in research; they measure 83.5–85.4% gold, somewhat lower.[2]
Historical Context
FACTKoban fineness began around 85% in the Keichō period, fell to the 50% range in Genroku, recovered to the 80% range from Hōei, then fell again from Genbun and stayed in the 50% range through Man'en at the era's end.[2]
FACTThe shogunate never published koban fineness; the public of the day could not know the exact standard.[2]
Manufacturing
FACTPeriod records (Goshoku Hikan) document the final "iroage" surface treatment (removing surface silver to raise gold concentration); for the Kyōhō Koban the recorded weight loss from iroage is 0.063%.[2]
Authentication Cautions
INTERPRETATIONNo single feature is known to prove authenticity on its own. Appraisal is a holistic judgment of features and provenance; third-party grades assess condition, not historical attribution. This section is educational.
Known Scholarly Issues
INTERPRETATIONDistinguishing the Kyōhō from the Shōtoku koban relies on the "hanare-Mitsutsugu" hallmark (光 and 次 separated) — a postwar, circumstantial diagnostic.[2]
INTERPRETATIONMintage and surviving population cannot be confirmed from the sources this record consults; we leave the unknown unknown.
Auction Records
No auction records confirmed for this exact coin type yet. Category-wide median prices are not shown as if they were prices for this type. Once confirmed, records will be listed here with auction house, sale, date, lot, grade, realized price (hammer vs. total), source URL, and review date.
References
- [1]「貨幣博物館 常設展示図録（江戸の金貨・改鋳）」（日本銀行金融研究所 貨幣博物館） — https://www.imes.boj.or.jp/cm/collection/tenjizuroku/mod/book/pageindices/index43.html（accessed: 2026-09-02）
- [2]上田道男 「江戸期小判の品位をめぐる問題と非破壊分析結果について」（金融研究 第12巻第2号（日本銀行金融研究所）、1993） — https://www.imes.boj.or.jp/research/papers/japanese/kk12-2-4.pdf（accessed: 2026-09-02）規定品位比較（第1表）・実測量目（第3表）・電子線励起X線分析（第4表）・色揚げ重量減（第2表・吾職秘鑑）。内部引用は本論文経由の孫引き。