Nibukin is a kind of gold coins that was distributed in the Edo period.
The formal name was nibuban, however after the issue of ichibu gin silver coin in 1837, it was also called 'nibukin'.
It was rectangular reed-shaped coin. On the surface, Gosan no Kiri mon (paulownia patterns) was engraved in a fan-shaped frame at the top and a word 'nibu'was engraved at the center.
Gosan no Kiri mon was engraved at the bottom.
A signature of 'Koji' and Kao (written seal mark) were engraved on the back side and casting era name was engraved at upper right position on some kinds of coins.
The face value was nibu and the currency value was equivalent to 1/2 ryo or 8 shu.
The first issue was in 1818 and it was casted until 1869 after Meiji Restoration.
It is said that new currency 'yen' was determined according to the currency standard that 1 ryo (2 coins) of Manei nibukin = 1ryo (2 coins) of Meiji nibukin = (new currency unit) 1 yen gold coin. This is also because the total of content and purity of gold of nibukin was close to substance value of one gold US dollar.
Shinbun nibuban started to be casted from April in 1818 and issued from June 10 of the same year, which was nibuban with a kaisho-tai (square (block) style of writing) letter 'bun' on the back side and also called shinji nibukin. Shinbun nibuban had half the ryome (weighed value) of Genbun koban (which was in circulation at that time), and it was 14% lower in terms of its karat value; it was positioned as a subsidiary currency since it was issued to make a profit through recoining. However, as Bunsei koban (which was to be issued the following year) was the same karat as nibukin and double ryome, advance notice of the upcoming issuing of the Bunsei koban was given.
There was also a pretext to exchange Genbun koban for free which had been distributed for more than 80 years becoming damaged.
Buichikin that was casting commission of kin-za (an organization in charge of casting and appraising of gold during the Edo period) was 1000 ryo for Toryo (leader) and 10 ryo for assistant manager and 4 ryo 3 bu for fukisyo toryo like the case of Genbun koban.
The distribution was stopped in November, 1835.
Sobun nibuban was issued on January 2, 1829 during the Bunsei era as Shinbun, the ryome was also same as Shinbun nibuban, however the karat was even lower to earn profit by recasting. A letter 'bun' was also engraved on the back side, however the style was sosho-tai (cursive style writing), therefore it is also called soji nibukin.
The buichikin was same as Shinbun nibuban.
The distribution was stopped on September 10, 1842.
Ansei nibuban was started to be casted from June, 1856 and issued from July 29 of the same year and the ryome was 1/2 of Tenpo koban, however the karat was only over 1/3, low karat gold coin next to isshukin to earn profit by recasting. There was no casting era name engraved on it.
The distribution was stopped in July, 1867.
Manen nibuban was issued from May 30, 1860 and the ryome of two coins was more than Manen nibuban that was issued at the same time, however it was nominal money having the least content of gold through the Edo period and the issued amount was much more than Manen koban taking initialtive of gold coin distribution and it was positioned as standard coin in effect in place of koban. When Kanjo bugyo (commissioner of finance) Tadamasa OGURI planed construction of Yokosuka Iron Factory, he tried to cover the cost by the profit of recasting nibuban, therefore it was also called Oguri nibukin.
The distribution was stopped at the end of September, 1874 at discontinuation of old gold and silver.
Kaheishi nibuban was casted for 10 months as a progress measure until opening of minting authority when the New Meiji Government took over kin-za in 1868 and is called Meiji nibukin. It is recorded that 608,000 ryo of the total casted amount 3,809,643ryo 2bu was nibukin with low karat. It was recorded that the karat was 170 monme (25.88% gold) in the early times and later it was changed to 240 monme (18.33% gold), however an example in Mint Museum has 200 monme (22.00% gold), which is considered as common. Also from the end of the Edo period, each domains were in economic difficulties, therefore forged nibukin were distributed and it is considered that existing silver coins with gold finish are some of those.
The distribution was stopped at the end of September, 1874 as Manen nibuban.
In the collecting world, if the upper part of the letter 'bu' (分) of 'nibu' (二分) which was engraved on the surface of the coin did not end with a upward brushstroke ('tomebu'), it was considered to be a Meiji nibukin and if it did end with an upward brushstroke ('hanebu'), it was considered to be a Manen nibukin. It is because gold plating silver coins are considered as lower rank nibukin of kaheishi which are mostly with 'tomebu'. The example of standard karat of Manen nibukin in Mint Museum is 'tomebu', however it was engraved 'rokko no san' (the third of six) and the others are not existing, therefore it is not considered as the evidence. There is another theory that is gradually becoming more popularity: since there are a lot of extant 'tomebu' that had been considered to be Meiji nibukin, they are now considered to be Manen nibukin, which had a greater circulation, and few extant 'hanebu' are considered to be kaheishi nibukin (Meiji nibukin).