coins

Battle of Sekigahara in 1600.
Hegemony of the Tokugawa was determined by the victory of this battle.

And Tokugawa got most gold and silver mines nationwide.
Following year，This monetary system was started.

Gold mine of Echigo Sado Island in particular.
Here was mined gold and silver in Japan's largest amount.
It became the basis of this monetary system.
　
But mined amount was carried out gradually decreased by a variety of circumstances.
(For example，Water accumulated in the mine shaft.)　
And economic activity of nationwide became active in inverse proportion.
As result absolute amount of coins has been missing.　
(Koban in particular.)
　
"Reduce the content of gold in Koban."　
1695,  Finally Tokugawa government made ​​this decision.　
　
　
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By the way，Coins of the first of Tokugawa regime.
It was something like the following.　

Bu(分) of one-quarter of ryō.
Its gold content was same with ryō.　

Chōgin(丁銀)
This was silver coin.
But its weight was not constant.
(about 43 monme/about 161,25g）
And its silver content of 80%

Mameitagin（豆板銀）
This was also silver coin.
And its weight was not also constant.
(One-tenth of chōgin basically)

This two silver coins was currency by weight.
It was used in combination.

Of course there was copper coins as a currency unit of its less.
However，At first Tokugawa regime used copper coins of before them.
　
And therefore quality of its coins was not constant.
Its negative effects went spread gradually.

Gold coins, silver coins, copper coins.
Its exchange rate has been determined in 1609.
　
1636，Tokugawa was casting a copper coin of uniform quality.
It called "Kan'ei tsūhō".(寛永通宝)