Ichibu kin gold coin (一分金)
Ichibu kin gold coin was a kind of gold coin that was distributed in the Edo period. The official name used in kin-za (an organization in charge of casting and appraising of gold during the Edo period) was ichibu ban, which also appeared in "Sankazue" (Picture Collection of Three Coins: History of Coinage in Japan) using different Kanji character, 一歩金. On the other hand, ancient coin books such as "Kinginzuroku" (Gold & Silver coin catalog) and "Dainihon Kaheishi" (Great History of Japanese Coins) called it with the name 'ichibu bankin' 一分判金/壹分判金 and this name was widely used in currency collecting world. After the issue of ichibu gin silver coin in 1837, the name 'ichibu kin' spread to distinguish from the gin silver coin.
Summary
The shaped was rectangle. On the surface, Gosan no Kiri mon (five & three paulownia patterns) was engraved in a fan-shaped frame at the top and a word 'ichibu' at the center and Gosan no Kiri mon was engraved at the bottom. On the other hand, a signature of 'Koji' and Kao (written seal mark) were engraved on the back side. That was a seal of Koji GOTO from kin-za who under took casting. Depending on the casting period and kind, the era name of casting was engraved at upper right position.
It was ichibu at face value. The currency value was equivalent to 1/4 ryo or 4 shu. Through the Edo period, it was casted and distributed as key currency with koban (former Japanese oval gold coin) and the purity of gold was same as koban issued in the same period and the ryome (a weighed value) was 1/4 of koban.
The total casting amount including koban and ichibu bankin was recorded in 'ryo' and they had a character of standard coin.
On the other hand, isshu kin, nishu kin, nibu kin were more like subsidiary currencies having less purity compared to the face values, however, nishu bankin issed in the Genroku period had a character of standard coin like ichibu bankin. In western Japan, a familiar name 'kotsubu' referred to mameitagin (name of a small round-type of silver coin in the Edo period), but in eastern Japan it referred to small rectangular gold coin.
In 1601, it was issued for the first time and after that since 1860, 10 kinds were casted and according to the economic status of Edo bakufu and the market, the karat and ryome (a weighed value) were revised as koban. Also in the late Edo period, ichibu gin silver coin which had equivalent face value as ichibu kin gold coin was issued and after that the issued amount of ichibu kin decreased dramatically.
Types
Issue year, ryome, content percentage of gold (regulation) in parentheses
Issued amounts are included in koban.
Keicho koban Keicho ichibuban (around 1601, 1.19 monme [a unit of weight], 84.3%=>86.8%)
Genroku koban Genroku ichibuban (October 1695, 1.19 monme, 57.4%)
Hoei koban Hoei ichibuban (April 1710, 0.625 monme, 84.3%)
Shotoku koban Shotoku ichibuban (June 1714, 1.19 monme, 84.3%)
Shotoku koban Shotoku ichibuban (September 1714, 1.19 monme, 86.8%)
Genbun koban Genbun ichibuban (June 1736, 0.875 monme, 65.7%)
Bunsei koban Bunsei ichibuban (July 1819, 0.875 monme, 56.4%)
Tenpo koban Tenpo ichibuban (August 1837, 0.75 monme, 56.8%)
Ansei koban Ansei ichibu ban (June 1859, 0.60 monme, 56.8%)
Manen koban Manen ichibuban (February 1860, 0.22 monme, 56.8%)