a little confusing

"1ryō(1 gold coin) = silver coin 50 monme = copper coin 4 kanmon(貫文)"
1609，Tokugawa was determined as this about the exchange rate.

Monme was unit of weight.
(1 monme was about 3,75g )

Copper coin 4 kanmon was about 15000g.
15000 ÷ 4 = 3750
Therefore 1 kanmon is 1000 monme.

Incidentally 1 ryō is 4,76 monme.(about 17,85g)

"gold coin 17,85g = silver coin 187,5g = copper coin 15000g"
In short Tokugawa was determined as this about the exchange rate.


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By the way there was one problem.

Copper coin.
It was the smallest unit of the money　from old time.
Its 1 piece called 1 mon(文).

"1000 mon is 1 kanmon."
It was defined like this.
In other words,1 mon was 1 monme.

And money that is used primarily was this.

But it was various copper coins of the previous era.
Its quality was not constant.
People had to accept it.
Various negative effects naturally occured by it.
It was a factor that inhibits against the development of the economy.

Tokugawa were required to improve this problem as soon as possible.
1636，They were casting a copper coin of uniform quality.
It called "Kan'ei tsūhō".(寛永通宝)
　

・・・・・・・・・


And although this is a little confusing.
　
"1 kanmon is 1000 mon."
This called Chō sen-hō.（丁銭法）
　
"1 kanmon is 970 mon or 960 mon."　
How to count like this were also present.
This called Seihyaku-hō.（省陌法）

Tokugawa seems to have adopted this.
It seems to have been 1 kanmon at 960 mon.　
(But weight of 1 mon was 1 monme.)

960 × 4 × 3，75 ＝ 14400

"gold coin 17,85g = silver coin 187,5g = copper coin 14400g"
In short Tokugawa was determined as this about the exchange rate.


・・・・・・・・・
　

Silver coin 1000 monme called 1 kan・me.(貫目)
Copper coin 1000 monme called 1 kan・mon.(貫文)

In short，In this case kan(貫) seems a thousand.（千）

And although this is a little confusing.

Brass, iron.
Material of copper coin was not the only copper.

The late 19th century，When the Meiji Restoration.
About 70% of the currency in circulation.

It was 1 mon of copper coin of iron.