The Birth of the Ansei Koban: Emergency Recoinage on the Eve of the Opening of Japan
The Ansei Koban (安政小判) began to be minted by the Edo shogunate in Ansei 6 (1859). This period was one of upheaval, as pressure to open the country—intensifying since Commodore Perry's arrival—reached its peak and Japan was forced to open its doors to the international community. In particular, the Treaty of Amity and Commerce between Japan and the United States, concluded in 1858, meant that the major ports of Yokohama, Nagasaki, and Hakodate were on the verge of opening the following year. In advance of this opening, the shogunate carried out a recoinage of the traditional koban. As it turned out, however, the Ansei Koban became the last koban of "conventional size" before a more drastic recoinage was implemented to address the outflow of gold. Its gold fineness was 56.8%, roughly the same level as its predecessor the Tenpō Koban (天保小判), but its weight was significantly reduced to 8.97 g. This recoinage was a temporary measure in response to the looming gold-outflow crisis. However, the massive outflow of gold after the opening of the ports could not be stopped, and in the following year, Man'en 1 (1860), the smaller and lower-fineness Man'en Koban (万延小判) appeared. The Ansei Koban can truly be described as a gold coin that shone with a "final brilliance" just before Japan's monetary system reached a major turning point during the turbulent final years of the Edo period.
Basic Information and Visual Characteristics of the Ansei Koban
The Ansei Koban is oval in shape, measuring approximately 52 mm in length by 30 mm in width. This is noticeably smaller than its predecessor, the Tenpō Koban (approximately 60 mm × 34 mm), making its reduced weight immediately apparent. Its weight is 8.97 g and its gold fineness is 56.8%. On the obverse, the characters「壹两」are inscribed in the center, along with the Gotō family's「光次」monogram. On the reverse, the most important identifying feature of the Ansei Koban is the「正」countermark. The character「正」is rendered in regular script (kaisho) with a clean, upright style, making it an important clue for authentication. Because the gold fineness is close to that of the Tenpō Koban, the color is relatively similar, but the two can be readily distinguished by size and the countermark on the reverse. As the minting period lasted only about one year, the total number of coins produced was relatively small and circulation was limited. For this reason, individual coins show variation in the coarseness or fineness of the goza-me (筵目) texture and in the manner in which the countermarks were struck—a characteristic that sets this koban apart from others. This coin can be said to be a historical testament that quietly speaks to the tense political situation of the late Edo period and the turmoil in the monetary system.
Details of Gold Fineness and Weight: The Shogunate's Painful Decision
The gold fineness of the Ansei Koban was set at 56.8%, nearly the same level as its predecessor the Tenpō Koban (56.4%). However, its weight was significantly reduced to 8.97 g from the Tenpō Koban's 11.2 g—a reduction of approximately 20%. As a result of this reduction in weight, the pure gold content of a single Ansei Koban was limited to approximately 5.1 g. At approximately 52 mm in length by 30 mm in width, it is clearly smaller than the Tenpō Koban, demonstrating that the shogunate had effectively reduced the real value of its coinage. This reduction in weight was not merely a response to fiscal difficulties. The background lay in the significant difference between the gold-to-silver exchange ratio in Japan and that in Western nations. In Japan, the ratio was set at 1 part gold to 5 parts silver, whereas on international markets a ratio of approximately 1 part gold to 15 parts silver was the norm. Exploiting this discrepancy, Western merchants after the opening of the ports brought in large quantities of silver, purchased Japanese gold, and took it out of the country—a "gold outflow problem" that was becoming increasingly serious. In order to stem this outflow of gold, the shogunate made the painful decision to reduce the gold content of the koban while leaving its nominal face value unchanged. The Ansei Koban was the last "old-style koban" issued by the Edo shogunate, and it served as a bridge to the turbulent era that followed, leading to the collapse of the monetary system and the emergence of the Man'en Koban. Further information can be found in System and Overview of Edo Gold Coins.
The Opening of Japan and the Gold Outflow Problem: The True Intent of the Ansei Recoinage
The minting of the Ansei Koban is closely connected to the foreign-relations crisis of the late Edo period. The Treaty of Amity and Commerce between Japan and the United States, concluded in 1858, sealed Japan's opening to the world, and in Ansei 6 (1859) the three ports of Yokohama, Nagasaki, and Hakodate were opened. This brought an influx of Western merchants into Japan and marked the full-scale commencement of trade. However, this trade harbored a serious problem. At the time, Japan's gold-to-silver exchange ratio—1 part gold to 5 parts silver—was far removed from the international standard of approximately 1 part gold to 15 parts silver. Western merchants noticed this discrepancy and brought large quantities of silver, cheap by international standards, into Japan, exchanged it for Japanese gold, and took it out of the country. This gave rise to what was known as the "gold outflow problem," causing Japanese gold coins to flow rapidly overseas and bringing Japan to the brink of a domestic gold shortage. The shogunate was compelled to take emergency measures against this unprecedented crisis. The recoinage of the Ansei Koban was an expedient measure intended to temporarily suppress the gold outflow by reducing the amount of gold contained in the koban while keeping its nominal value unchanged. However, even this measure proved inadequate, and the outflow of gold could not be stopped. As a result, in the following year, Man'en 1 (1860), the Man'en Koban appeared with its gold fineness reduced even further. The Ansei Koban can be described as a symbolic coin of the late Edo period that bears witness to the severity of this gold outflow problem.
Authentication Points: The「正」Countermark and Other Identification Methods
The most important point in determining the authenticity of an Ansei Koban is the「正」countermark struck on the reverse. The character「正」is cleanly engraved in regular script (kaisho), and the balance between the upper「一」and the lower「止」, the length and angle of the horizontal strokes, and the overall placement of the character serve as criteria for authentication. In particular, close observation of characteristics unique to hand-engraving by a skilled craftsman—such as the vigor of the brushstroke-like incisions and the smoothness of the lines—is required. Verification of weight and dimensions is also essential. The Ansei Koban has a weight of 8.97 g and an oval shape measuring approximately 52 mm in length by 30 mm in width. By contrast, the Tenpō Koban, with which it is easily confused, has a weight of 11.2 g and measures approximately 60 mm × 34 mm—clearly different in both size and weight. For coins that have undergone considerable wear, visual judgment alone is difficult, and it is indispensable to measure using a precision scale (a scale with ±0.1 g accuracy is recommended) and calipers. The depth of the engraving of the「壹两」characters and the「光次」monogram on the obverse, as well as the coarseness or fineness of the goza-me texture, also serve as aids to authentication. Because the minting period for the Ansei Koban was short, there is a tendency for greater individual variation in goza-me patterns compared to other koban. A comprehensive assessment of these characteristics leads to reliable authentication. More detailed information can be confirmed at Japanese Coin Counterfeit Detection Guide.
Comparison with the Tenpō and Man'en Koban: The Evolution of Late Edo Gold Coinage
The Ansei Koban occupies a position like a "bridge" between the Tenpō Koban and the Man'en Koban during the period of monetary confusion at the end of the Edo period. By comparing these three coins, one can clearly understand the progression of the shogunate's responses to the fiscal crisis and the gold outflow problem it faced. First, the predecessor Tenpo Koban began to be minted in 1837 (Tenpō 8), with a gold fineness of 56.4% and a weight of 11.2 g. It circulated in very large quantities and was widely used as the primary koban of the late Edo period. By contrast, the Ansei Koban appeared in Ansei 6 (1859), with gold fineness slightly raised (56.4% → 56.8%) while weight was drastically reduced from 11.2 g to 8.97 g. This was a temporary measure to cope with the gold outflow resulting from the opening of Japan. Then, in the following year, Man'en 1 (1860), as the gold outflow became even more severe, the Man'en Koban was minted with both a significant reduction in size and a decrease in gold fineness. The Man'en Koban maintained a fineness of approximately 57% (according to catalog records) while its weight was reduced to 3.3 g—a dramatic reduction to nearly one-third of the Ansei Koban's weight of approximately 9 g. Viewing these three coins side by side in this way, one can visually understand that the progressive miniaturization and reduction in fineness of gold coinage advanced in stages during the final years of the Edo period. Possessing this series of koban as a set constitutes a valuable body of evidence for the economic history of the dawn of Japan's modernization.
Notes on Counterfeits and Altered Coins, and a Guide to Detection
Because the number of Ansei Koban minted was relatively small, the absolute volume in circulation on the market is limited. For this reason, the risk of sophisticated counterfeits is less of a concern for collectors than the problem of misidentification arising from "confusion with the Tenpō Koban" or "altered coins." Because the gold fineness of the two is similar, distinguishing between them visually can become difficult, particularly with coins that have suffered heavy wear or damage. When distinguishing between the Ansei Koban and the Tenpō Koban, it is important first to understand the clear differences in weight (Ansei Koban 8.97 g vs. Tenpō Koban 11.2 g) and size (Ansei Koban approximately 52 mm vs. Tenpō Koban approximately 60 mm). Always use a precision scale and calipers to confirm these figures accurately. The「正」countermark on the reverse is also the definitive identifying mark of the Ansei Koban. As for sophisticated counterfeits, cases have been reported of alterations such as affixing gold to the Man'en Koban to increase its weight, or falsifying countermarks. Such altered coins can be difficult to detect without a detailed examination by an expert. When considering a purchase, it is wise to use a reputable coin dealer or authentication institution, and where possible to select a coin that comes with a certificate of authentication, in order to avoid risk. Please also refer to Reading Calligraphy Styles.
Position in the Collecting Market and Assessment of Rarity
The Ansei Koban had a minting period of approximately one year, and the total number minted was limited to approximately 2,200,000 ryō. Compared with the estimated approximately 8,000,000 ryō for the preceding Tenpō Koban and approximately 12,000,000 ryō for the succeeding Man'en Koban, its rarity stands out. Due to this limited circulation, the Ansei Koban is assessed as having "moderate rarity" within the overall koban collecting field. Prices in the collecting market fluctuate considerably depending on condition. The Ansei Koban, as a coin issued at a historical turning point—specifically the opening of Japan and the gold outflow problem—during the turbulent final years of the Edo period, commands steady demand from history enthusiasts and collectors with an interest in late Edo history. It is frequently collected as part of a comparative set with the Man'en Koban and Tenpo Koban, and its historical value as a precious document illustrating the evolution of the late Edo monetary system is reflected in its market price. Individual prices and auction results are posted in the market records only when verified records—including event, lot, source URL, and date of confirmation—have been obtained.