Tenpō Chōgin — The Lowest Purity Silver Coin Born During the Reform Era

In 1837, the eighth year of the Tenpō era, the shogunate's financial difficulties became severe. The Ōshio Heihachirō Rebellion, which broke out in Osaka that year, further highlighted the unstable fiscal situation of the shogunate. Mizuno Tadakuni pushed forward with the Tenpō Reforms and decided to mint silver coins as a part of fiscal reconstruction. At that time, a review of the currency system was imperative for the Edo shogunate, which urgently needed to rebuild its finances. Mizuno Tadakuni chose not to follow the high purity standard set by the Keichō Koban minted in the Keichō era and significantly reduced the purity. As a result, the silver purity dropped to 26.96%. This had the effect, as seen in the types of Edo gold coins and their identification, of shaking confidence in the currency at the time. Mizuno Tadakuni had to take such measures to solve the shogunate's fiscal difficulties. Additionally, as part of the Tenpō Reforms, land redistribution and restrictions on commercial activities were implemented, having a significant impact on the overall economy. Although the issuance of the silver coins was intended to stabilize finances, contrary to the shogunate's intentions, it caused public anxiety and economic turmoil.

The minting of the Tenpō Chōgin was overseen by the Gotō family, who managed the Ginza and had a reputation for expertise in coin minting throughout the Edo period. The Gotō family's technical prowess was considered the best in Japan at the time. However, an unprecedented measure was taken in the minting of the Tenpō Chōgin, with the decision to considerably lower the purity of silver. This was influenced by a shortage of silver supply and fluctuations in copper prices, resulting in a composition of 26.96% silver and 73.04% copper. This combination was challenging even for the technicians of the time. In the Ginza, new technologies were introduced to enhance minting efficiency, and craftsmen utilized these techniques to engage in mass production. Although silver refining technology evolved and alloying with copper advanced, the drop in purity was unavoidable, and the resulting chōgin had a dulled luster and increased weight compared to previous coins, making it easily recognizable to the populace. These technical advancements influenced later currency reforms, leading to a reevaluation of silver purity during the transition to the Ansei Chōgin. Moreover, being the minting site, the Ginza was also a center of technological innovation in Edo's monetary circulation.

The appearance of the Tenpō Chōgin in the market caused ripples in the Edo economy. Due to its low silver purity, the Tenpō Chōgin was questioned for its reliability from the outset. In comparison to the previous Keichō Chōgin, its value was significantly lower, and exchange rates dropped substantially. For instance, one Tenpō Chōgin was said to hold only a third of the value of the same weight of Keichō Chōgin. As a result, merchants became cautious in their transactions, with many reluctant to accept the Tenpō Chōgin, leading to instability in prices. Particularly, prices for necessities like rice and salt temporarily soared due to the circulation of the Tenpō Chōgin. Ordinary people were bewildered by these changes, fostering dissatisfaction with the unstable currency system. In this environment, farmers and townspeople were forced to further economize to safeguard their livelihoods. As illustrated in the basics of coin auctions, the value and circulation of currency are deeply connected to the stability of society as a whole. The circulation of this currency persisted during the turmoil at the end of the Edo period and ultimately concluded with the emergence of the Ansei Chōgin.

The Tenpō Chōgin, as a symbol of the currency system's transition during the late Edo period, had a substantial impact on later generations. Although the circulation of the Tenpō Chōgin temporarily alleviated the shogunate's financial difficulties, it led to long-term economic turmoil. In response, the Ansei Chōgin appeared in 1859, leading to the gradual phase-out of the Tenpō Chōgin. By increasing its silver purity, the Ansei Chōgin aimed to restore currency trust, but it was too late, and trust in the shogunate had been greatly damaged. Nevertheless, the experience of the Tenpō Chōgin served as a lesson for the later Meiji government's modernization of the currency system. As shown in the value and identification of modern currency, the Meiji government proceeded with policies to unify the purity and weight of currency, enhancing reliability both domestically and internationally. Subsequently, the Tenpō Chōgin gained popularity among collectors, with its historical value re-evaluated. It serves as an important object of study, vividly illustrating the economic conditions of that time. Thus, the Tenpō Chōgin is essential not only as currency but also for understanding the economy and politics of the Edo period.