The Names Kyōhō Chōgin and Shōtoku Chōgin
This chōgin has different names in different sources. - Currency Museum catalogue and collection catalogue: "Shōtoku Chōgin" - Ministry of Finance record (1875): "Kyōhō silver" - Paper of the Bank of Japan Institute for Monetary and Economic Studies (2000): "Shōtoku silver" The Ministry of Finance record and the Institute's paper both give the start of minting as Shōtoku 4 (1714) and the amount minted as 331,420 kan. This shows that they refer to the same chōgin. The mameita-gin of the same period is listed in the collection catalogue as "Shōtoku Mameita-gin."
When It Was Minted, and Why
After the Genroku recoinage, prices rose. In 1714, on the proposal of Arai Hakuseki, the shogunate raised the fineness of gold and silver coins to the level of the Keichō gold and silver coins. This is called the Shōtoku recoinage (according to the Currency Museum). Arai Hakuseki served the 6th shōgun Ienobu and the 7th shōgun Ietsugu (according to the Currency Museum catalogue). According to the Institute's paper, minting ran from the 5th month of Shōtoku 4 (1714) to the 4th month of Kyōhō 21 (1736). It circulated until the 4th month of Genbun 3 (1738).
Fineness
The fineness is 80% (according to the Currency Museum catalogue). This is the same fineness as the Keichō Chōgin. The Hōei Yotsuhō Chōgin, minted just before it, had a fineness of 20%. The Shōtoku recoinage raised the fineness of chōgin from the 20% of the Hōei Yotsuhō Chōgin to 80% (according to the Institute's paper). According to the Currency Museum, the Shōtoku–Kyōhō recoinages were the only recoinages in the entire Edo period that raised the fineness of gold and silver coins. The year and fineness of each chōgin given in the Currency Museum catalogue are as follows. - Keichō Chōgin: 1601, fineness 80% - Genroku Chōgin: 1695, fineness 64% - Hōei Futatsuhō Chōgin: 1706, fineness 50% - Hōei Eiji Chōgin: 1710, fineness 40% - Hōei Mitsuhō Chōgin: 1710, fineness 32% - Hōei Yotsuhō Chōgin: 1711, fineness 20% - Shōtoku Chōgin (Kyōhō Chōgin): 1714, fineness 80% - Genbun Chōgin: 1736, fineness 46% - Bunsei Chōgin: 1820, fineness 36% - Tenpō Chōgin: 1837, fineness 26% - Ansei Chōgin: 1859, fineness 13%
How It Was Used as Money by Weight
Chōgin were silver coins used by weight. The unit was the monme; 1 monme is 3.75 g, or 10 fun (according to the Currency Museum catalogue). Money changers weighed silver with balances and weights (according to the same catalogue). For gifts and similar uses, silver wrapped in paper, called tsutsumi-gin, was also used. The unit "mai" was written on the wrapper; 1 mai is 43 monme. To match the weight, mameita-gin was sometimes put in together with chōgin (according to the same catalogue). The Institute's paper considers that chōgin varied in weight and were minted on the assumption that they would be used in wrapped packets.
Weight
The Institute's paper measured 12 Shōtoku Chōgin. The minimum was 95.31 g, the maximum 177.57 g, and the average 136.59 g. The paper reports that they are lighter than chōgin of other periods. The paper suggests that they may have been made lighter with the exchange rates against lower-fineness coins, such as the Genroku Chōgin, in mind. The rates were: against 1 kanme of Shōtoku silver, 1 kanme of Keichō silver, 1 kan 250 me of Genroku silver, 1 kan 538 me 4 fun 4 rin of Hōei Futatsuhō silver, and 2 kanme each of Hōei Eiji, Mitsuhō and Yotsuhō silver (according to the official notice of the time cited in the paper).
Afterwards: The Genbun Recoinage
In 1736, the shogunate lowered the fineness of gold and silver coins. This is called the Genbun recoinage. The fineness of the Genbun Chōgin is 46% (according to the Currency Museum catalogue). According to the Currency Museum, this recoinage was carried out to counter the fall in rice prices caused by the Shōtoku–Kyōhō recoinages and to increase the amount of gold and silver coins in circulation. It was not aimed at fiscal revenue. Shōtoku silver circulated until the 4th month of Genbun 3 (1738) (according to the Institute's paper).
How to Check a Coin in Hand
Chōgin vary in weight from piece to piece. Weight alone is not enough to judge a piece. The Currency Museum's collection catalogue shows images of Shōtoku Chōgin. Compare the shape of the stamps with the images in the catalogue. To judge whether a coin is genuine, an appraisal by a specialist is the reliable way. How to spot forgeries is covered in An Introduction to Spotting Forgeries. For related entries, see The World of Chōgin, Keichō Chōgin, Genroku Chōgin, Hōei Yotsuhō Chōgin and Genbun Chōgin.