recast

But production of silver fell already in the mid-17th century.
Tokugawa finally banned the export of silver in 1668.
　
"1ryō is silver coin 60 monme."
And Tokugawa changed the exchange rate in 1700.

60×3，75×0，8＝180g
Gold 15、492015g = Silver 180g
180 ÷ 15、492015 ＝ 11、6188888275

Gold 1 : Silver 11、6188888275

Price ratio became this.
Probably Tokugawa tried to adjust with the market rate on this occasion.
(Of course unchanged after this，Market was the rate fluctuations system.)


・・・・・・・・・


By the way,Little before this, In 1695 Tokugawa has recast the gold and silver coins.(改鋳/Kaichū )
　
Second half of the 17th century，Gold production was also fell as with silver.
By contrast，Japan economy was continuing to expand.
　
Amount of coins itself.
It became insufficient.
　
"Lower the content of the coins.
And increase the amount of coins in circulation in the market."
This recast was done in this intention.　
　
Gold 15、492015g = Silver 180g
Therefore,Calculation based on this is wrong.
However,content ratio seems was not changed.
Gold and silver were lowered at the same rate.

Gold 1 : Silver 11、6188888275
Price ratio at that time would not be wrong in this.
　

・・・・・・・・・

　
According to it.
First gold coin called "Keichō-Koban".(慶長小判）

This seems to not know the total production by burned documents.
　
But amount of its recast.(引替/Hikikae)
This has been found.
Probably this recast was as "Keichō-Koban".　
There is no change in the content of the gold.　

Incidentally there is name of an era in Japan called "Gengō".(元号)　
Date separator is different from the the Christian era.

"1606-1694(not accurate)
Amount of recast of keichō-koban is 10,527,043 ryō."
　
Gold 15,492015g　
Gold 1g was ¥ 4,245.(as of Jun 17, 2013 19:15)　

When calculated in this number.

10527043 × 15,492015 × 4245 ＝ 692296283718　

Amount of gold coin recast of 1606-1694
Gold 163085108g (rounded)
￥692,296,283,718