Updated: Nov 27, 2021
This large bronze coin has been identified as a Tenpō Tsūhō. The Tenpō Tsūhō was introduced during the 6th Year of Tenpō (1835), under the reign of Emperor Ninkō (1800-1846). They remained in circulation during the closing phase of the Tokugawa Shogunate, better known as the Edo period. Ending with the Meiji Restoration (1968), which introduced the Japanese Yen.
A single Tenpō Tsūhō was valued at 100 Mon or 1/40th Ryō. The coin's dimensions are 49 mm (1.93 in) long, 32 mm (1.26 in) wide, and 2.6 mm (0.106in) thick. The average Tenpō Tsūhō weighs a hefty 20.7 g. The usual alloy composition contains 78% Copper/12% Lead/10%Tin. Notably the large size, weight, and general age of the Tenpō Tsūhō. Has historical made them desirable as good luck charms up to the modern age.
The observe is simple and practical, featuring 4 Kanji characters arranged in pairs. The upper Kanji read "天保" or Tenpō, a reference to the era of circulation. While the lower Kanji read"通寳" or Tsūhō, meaning "circulating currency/treasure". Poetically, one possible interpretation of Tenpō Tsūhō can be "circulating treasure of the Tenpō era".
Similar to large Chinese cash coins, center features a squared hole with a thick rim. This inner rim is roughly as the outer primary rim. The inner observe face has a somewhat sand-like texture, owning to it's casted nature. Wear lines from general circulation, can be seen throughout the coin's raised surfaces.
The reverse is for the most part similar to the observe, although with different symbols. The upper area features the Kanji "當百" or Tō Hyaku, a reference to it's 100 Mon value. While the lower area features a Kaō, an eastern form of signature. This particular Kaō belongs to master engaver Gotō San'emon. Who was appointed by Shōgun Tokugawa Ieyasu (1543-1616 CE) to oversee the Edo mint, in 1601. Gotō San'emon's Kaō was later ceremoniously used by his descendants.
As the Gotō family oversaw the Kinza, the Shōgun's sanctioned gold monopoly/guild. Which regulated the value of minted coins. By design, all "mother coins" were created by the Kinza mint in Edo (now known as Tokyo). Thus all sanction coinage featured the Gotō family's Kaō. Which in turn were replicated by other smaller mints throughout Japan.
These smaller mints had their own mint marks, known shirushi (印). Which can be found along the coins rim. Identifying these tiny mint marks is a specialized numismatic field itself. Many are abstract in nature, representing leaves and flowers. And can be easily mistaken for simple damage, as they're struck rather than cast.
The similar Ryūkyū Tsūhō (琉球通寳) closely resembles the Tenpō Tsūhō and was face valued at 100 mon.
Ryūkyū Tsūhō can be differentiated who Tenpō Tsūhō by their lack of a Kaō. Instead featuring the Kanji 百 (Hyaku) takes it's place.
Some Tenpō Tsūhō are reproductions, made by the Ezaki Glico candy company. Who in the 1950s began giving genuine Tenpō Tsūhō as prizes.
To meet increasing demand Ezaki Glico produced their own reproductions. Which due to scarcity, are even more valuable than some genuine Tenpō Tsūhō.