Tenpō Tsūhō — The Ambition and Forgery Storm of 'Tōhyaku Sen' Created by Financial Crisis

The Great Tenpō Famine that began in Tenpō 4 (1833) is recorded as the largest poor harvest in the Edo period. In the rural areas of Tōhoku and North Kantō, rice harvests plummeted to mere fractions of normal years, reportedly resulting in tens of thousands of deaths from starvation (various theories exist). Seeking employment, migrants left rural areas, flooding into Edo and Osaka, deteriorating urban security.

The shogunate's finances were already in a critical state by this time. The lengthy rule of the 11th shogun Tokugawa Ienari over 50 years, known as the "Era of the Grand Daimyo," allowed opulent culture to flourish but led to chronic fiscal deficits. Expenses from activities such as maintaining the Ōoku, entertaining daimyo, and temple and shrine repairs overlapped, and famine relief costs added to this burden.

In Tenpō 7 (1836), uprisings occurred in Matsumae Domain and Mikawa Kamo, and in Tenpō 8 (1837), the Ōshio Heihachirō revolt erupted in Osaka. Although the Ōshio rebellion was suppressed within a day, it planted widespread distrust in the shogunate's governance capabilities.

As a solution to this crisis, the issuance of new coins with dramatically increased face value emerged. If a single coin could replace the value of 100 circulating Kan'ei Tsūhō (a mon coin), copper consumption could be saved, and surplus could be added to finances. After trials in Edo's coin mint (Fukagawa) in Tenpō 6 (1835), full-scale minting began in Tenpō 7 (1836). The approximately 49mm x 33mm oval shape was intended to distinguish it from the circular Kan'ei Tsūhō, and this large coin was referred to by the common people as "manjū coin (manjū zeni)."

The actual weight of the copper significantly fell short of the nominal value (tōhyaku mon), and this discrepancy became a hotbed for the later spread of forgery. Although the shogunate used the surplus to supplement finances, the contradiction of issuing high-value coins lacking credit became the root cause of confusion surrounding the Tenpō Tsūhō thereafter.

Soon after the Tenpō Tsūhō began minting under shogunate leadership, Mito Domain lord Tokugawa Nariaki applied for permission from the shogunate to mint within the domain. Known as an advocate of the Sonnō Jōi ideology, Nariaki was also a realist administrator who focused on the financial reconstruction of the Mito Domain. Despite being a prestigious domain with 300,000 koku, the Mito Domain suffered from chronic financial difficulties and needed an independent source of income.

Nariaki's application was approved, and minting in the Mito Domain began between Tenpō 7-9 (1836-1838), according to some theories. The Tenpō Tsūhō minted in Mito was known as "Mito Sen," gaining a certain trust for its elegant script and quality.

The Mito Domain's precedent became a catalyst for extending permission to other domains grappling with financial issues. Domains like Sendai, Morioka (Nambu Domain), Kaga, and Satsuma applied for minting permissions, and the shogunate approved these under conditions of paying a stipulated levy and adhering to procedures. It is believed that over ten domains obtained permission towards the end of the Tokugawa period.

As 'han-minting' spread, the quality of circulating Tenpō Tsūhō began to vary significantly. Records indicate lightweight coins below the stipulated weight (approximately 5 momme 3 bu) and poor-quality items with copper purity below standards. Though the shogunate set weight regulations, management didn't reach remote areas. In the collectors' world, Mito Sen from this era is especially treasured. Early Mito Sen from Nariaki's rule is famous for its beautiful script, with well-preserved pieces receiving high valuations even in the modern market.

Early Mito Sen is renowned for its copper quality and refined script, clearly distinguishable in weight and style from later 'han-minted' items and forgeries. This quality disparity underpins the Mito Sen premium in today's collectors' market.

In Tenpō 12 (1841), Senior Councilor Mizuno Tadakuni implemented the "Tenpō Reforms." The three main pillars included a frugality decree, policing of morals, and the dissolution of merchant guilds, with the dissolution aimed at stabilizing prices. At the time, Edo harbored a deep economic disparity between wealthy merchants and impoverished farmers, which bred social unrest, compelling the shogunate to take action.

Mizuno's goal was "price stabilization." However, the dismantling of merchant guilds and trade unions disrupted distribution functions, paradoxically destabilizing prices. The mass circulation of Tenpō Tsūhō exacerbated the confusion during this period. Although officially, 100 mon of face value equaled 100 Kan'ei Tsūhō coins, in practice, the equivalent value varied between 90 to 100 mon depending on the region, complicating commercial transactions.

The fundamental contradiction of the Tenpō Reforms lay in tacitly permitting "currency value inflation" as a solution for fiscal deficits, while simultaneously attempting to curb the resulting price hikes with separate measures. The currency policy of the reforms failed to delve into a fundamental resolution.

In Tenpō 14 (1843), Mizuno was toppled over fierce opposition from daimyo and hatamoto regarding the jōchi-rei, a policy changing daimyo and hatamoto lands surrounding Edo and Osaka into direct shogunate control. The Tenpō Reforms collapsed after little more than two years, and merchant guilds were restored. Thereafter, shogunate politics lacked consistent leadership through the Kaei, Ansei, and Bunkyū eras. The minting of Tenpō Tsūhō continued until the late Tokugawa period, and the quality and quantity of circulating coins remained chaotic moving into the Meiji era.

Following Mizuno's fall, the shogunate lost consistency in fiscal policy, and throughout the Ansei and Bunkyū periods, makeshift expansions of minting and quality downgrades persisted. The mass issuance of Tenpō Tsūhō was a product of this political floundering and contributed to the economic turmoil that characterized the late Tokugawa period.

A major issue the Tenpō Tsūhō faced was the rampant forgery. With a face value of 100 mon, a high nominal value meant significant profits could be made even when manufactured with inferior copper. From the late Edo to the Bakumatsu period, rural metalworkers and unauthorized operators established secret mints, producing and circulating forged Tenpō Tsūhō coins that were underweight and low-grade.

The shogunate erected warning signs against forgery in various regions and imposed severe penalties on detected counterfeiters. However, detection was challenging, and identifying the production site was difficult. In many cases, distinguishing between domain-minted and counterfeit coins was visually challenging, requiring merchants and commoners to possess knowledge to assess the weight and script of Tenpō Tsūhō themselves. The "opacity of authenticity" heightened the mistrust of Tenpō Tsūhō entirely.

Forgery extended to Kan'ei Tsūhō as well. The customary mixing of Tenpō Tsūhō with these forged coins complicated late Edo period currency circulation significantly. In Osaka's money exchanges and Edo's coin dealerships, independent conversion rates for Tenpō Tsūhō emerged. The discrepancy between "the façade 100 mon" and "the actual ○ mon" became a daily occurrence.

After Meiji 2 (1869), the new government hastened to establish a modern monetary system. However, the retrieval of the old coins was an enormous task, necessitating continued circulation of Tenpō Tsūhō and Kan'ei Tsūhō for the time being. In Meiji 9 (1876), the government finally declared the prohibition of both Tenpō Tsūhō and Kan'ei Tsūhō, bringing the 40-year history of Tenpō Tsūhō to a close. The coinage system that supported the Edo period's three currency system was fundamentally shaken by the overproduction of Tenpō Tsūhō, prompting a transition to the modern monetary system.