What Is the Kyōhō Koban: The Shōtoku-Kyōhō Recoinage and Recorded Purity and Weight

The Kyōhō Koban is a gold coin from the Edo period, first minted in 1715 (Shōtoku 5). According to the "History of Japanese Currency" by the Currency Museum of the Bank of Japan, it was issued by the shogunate to enhance the coin’s purity further following the Shōtoku Recoinage in 1714, which was in response to Arai Hakuseki’s proposal.

Background and Characteristics of the Kyōhō Koban

The Kyōhō Koban, minted starting in 1715 (Shōtoku 5), is a gold coin. According to "History of Japanese Currency" by the Currency Museum, the Edo shogunate executed a recoinage in 1714, raising the fineness to match that of the Keichō gold and silver coins in response to rising prices after the Genroku Recoinage, prompted by Arai Hakuseki (Shōtoku Recoinage). In the following year, 1715, the coin's purity was further enhanced (Kyōhō Koban). The permanent exhibition catalog states that the recoinage was advanced by Arai Hakuseki, who served the 6th shogun, Ienobu, and the 7th shogun, Ietsugu. Tokugawa Yoshimune became the 8th shogun in Kyōhō 1 (1716), which was after the start of Kyōhō Koban minting (1715). Therefore, the Kyōhō Koban belongs to the Shōtoku-Kyōhō Recoinage promoted by Hakuseki, not to Yoshimune’s "Kyōhō Reforms".

The catalog notes the fineness of the Kyōhō Koban as 87% and a weight of 18g (both rounded values), surpassing the 84% of the Keichō and Shōtoku Kobans. According to Michio Ueda's paper (Kin'yu Kenkyu, 1993), the regulated fineness in the Kinza records series is 50.7 koi (86.79%). Regarding the outcome of the recoinage, the "History of Japanese Currency" by the Currency Museum notes that it abruptly decreased the currency supply, causing economic stagnation and a decline in prices.

The "History of Japanese Currency" also states that in 1736, the shogunate reduced the fineness of gold and silver coins (Genbun Recoinage) to counteract declining rice prices from the Shōtoku-Kyōhō recoinages. The Shōtoku-Kyōhō Recoinage is noted as the only instance of increased gold and silver fineness in the Edo period, according to the "History of Japanese Currency". Definitive records of the minting volume are unavailable. Further details on this coin are elaborated in Kyōhō Koban.

The Kyōhō Koban is positioned within the Edo period’s currency policy of raising fineness lowered during the Genroku Recoinage through the Shōtoku-Kyōhō Recoinage and then lowering it again during the Genbun Recoinage (Currency Museum "History of Japanese Currency").

Historical Background and Evaluation of the Kyōhō Koban

The Kyōhō Koban, with an 87% fineness (rounded, catalog figure), is recorded with the highest purity among kobans in the permanent exhibit's recoinage table. The name "Kyōhō" is derived from the era name, but minting began in Shōtoku 5 (1715) (catalog).

The weight is recorded as 18g (rounded) in the catalog, the same as the Keichō Koban. The surface bears the kaō and the stamped "壹両" (one ryo). According to the permanent exhibition catalog, gold coins were produced under the instruction of the Gotō family, and the manufacturing facility within the Gotō office grounds in Nihonbashi became known as the gold mint.

Regarding differentiation from the Shōtoku Koban, Michio Ueda’s article (Kin’yū Kenkyū, 1993) references the "hanare Kōji" ("光" and "次" separated stamp) and classifies it as circumstantial evidence proposed after the war.

Auction records confirming a Kyōhō Koban have not been found in the current records of Ittendo's market. The overall market value of the same type is not disclosed as the price of this variety. Verified records will be included with auction house, event, date, lot, grade, auction price, source URL, and verification date upon confirmation.

For more related information, please refer to the pages on Keichō Koban and Genroku Koban.

Factors Determining the Value of the Kyōhō Koban

The Kyōhō Koban features a recorded purity of 87%, the highest compared to the Keichō and Shōtoku Kobans at 84%, Genroku Koban at 57%, and Genbun Koban at 66% (all rounded values). Its weight matches the Keichō, Genroku, and Shōtoku at 18g, while the Genbun Koban weighs 13g (catalog).

When examining an individual piece, key indicators include the kaō on the surface, the "壹両" stamp, stamp shape, and weight. The catalog’s recorded weight of 18g (rounded) can serve as a benchmark for verification. According to Michio Ueda’s article (Kin’yū Kenkyū, 1993), non-destructive analysis of three samples held by the Bank of Japan Financial Research Institute revealed gold content between 85.7% and 86.6% and weight ranging from 17.70 to 17.75g. No documentation consulted indicates that high purity results in reduced tarnishing or rusting. Evaluation involves synthesizing multiple characteristics and provenance; no conclusions can be drawn from a single feature. General precautions for identifying counterfeit or altered items can be referenced in the Guide for Detecting Fakes and Alterations.

Individual prices and auction cases will only be published in market records once confirmed to align with verified Kyōhō Kobans. Authenticity verification involves comparing stamps, kaō, and weight with catalog and records data.

Important Checks for Acquiring and Owning the Kyōhō Koban

Key points to verify when acquiring and owning a Kyōhō Koban are summarized. There are no definitive records confirming minting volumes or the number of existing pieces. The condition view should align with Standards for Grading Ancient Coins.

Next, the interpretation of auction records is crucial. No confirmed auction records matched to the Kyōhō Koban exist yet in Ittendo’s market records, so general data for the entire type will not be presented as the price for this coin type. For reading auction records, consult Introduction and Usage of Ancient Coin Auctions, and check the records directly through Auction History Overview.

Coins should be stored properly, following guidelines in Proper Storage Methods for Ancient Coins. Avoid humidity, temperature fluctuations, and physical impacts.

Historical Significance and Precautions of the Kyōhō Koban

The Kyōhō Koban is documented with the highest purity (87% rounded) in the recoinage table from the permanent exhibition catalogs of Edo-period kobans. It is part of the Shōtoku-Kyōhō Recoinage led by Arai Hakuseki, not associated with Yoshimune's "Kyōhō Reforms" (catalog).

The presence or methods of forging or modifying counterfeit items cannot be confirmed from the consulted materials and thus are not addressed in this article. Examining an individual piece involves cross-referencing stamps, kaō, and weights with catalogs and records, aligned with provenance.

Cautious measures are advised for post-purchase storage. Moisture or abrupt temperature changes and physical impact can result in degradation. Storing in specialized coin capsules or albums and keeping them in a dark place is recommended. For detailed storage methods, refer to Proper Storage for Ancient Coins. Keeping records of storage and assessments provides reference points for future validation.

When viewing the Kyōhō Koban, the key points are it being part of the Shōtoku-Kyōhō recoinage, its cataloged purity and weight, and the checking of stamps and kaō. Only verified records are included in market logs.