Isshukin (a kind of gold coin circulated during the Edo period) (一朱金)
Isshukin refers to a kind of gold coin circulated during the Edo period.
It was also called Isshuban, or Bunsei-Isshuban because of its issuance only in the Bunsei era, or Kaku-Isshukin from the shape.
Its shape was square. It had Gosan no Kiri mon (paulownia patterns) on the front face, and letters of '一朱' (Isshu) in the lower part of the front face.
On the reverse side, a signature, '光次' (Mitsutsugu; referring to Mitsutsugu GOTO who supervised kinza (an organization in charge of casting and appraising of gold during the Edo period) was marked.
Its face value was one shu (unit of currency, 16 shu = 1 ryo). Its currency value was equivalent to one sixteenth of ryo and a quarter of bu (unit of currency, 4 bu = 1 ryo).
Since the amount of gold contained in one ryo against Koban (former Japanese oval gold coin) and Ichibuban was held down as well as Nishukin gold coin and Nibukin gold coin, Isshukin was used as subsidiary coin.
The purity of gold was lowest, and as well as other Koban and Bukin (gold coins), the enhancement of the color which dissolved silver on the surface was operated at the time of manufacture. However, it is said that a silver colored bare metal appeared immediately due to abrasion by circulation, and furthermore, Isshukin became as glossy as silver coins maybe because of solid diffusion when it suffered from a fire.
And, it was usual to strictly inspect ryome (a weighed value) (mass) for each Koban and Bukin during the manufacturing process, but for this Isshuban, ryome was inspected only for every bunch of five ryo or ten ryo.
The minting started in May 1824, and the first coin was issued on July 27 of the same year, but Isshukin was not popular because of low purity of gold, its color looking like a false gold coin and fragility, and also because it was lost easily due to a small size and difficulty in handling.
The minting ended in 1832, and the circulation ceased at the end of September 1840.
After that, as a currency with a face value of one shu, Isshugin (silver coin) came to be used instead.