Japan used copper and iron coins called mon from 1336 to 1870 as currency, with the character for mon meaning "coin". These coins had a hole in the middle to string them together and circulated alongside silver and gold ingots. Throughout Japanese history there were many different styles of currency varying in shape, size, design and material including gold, silver and bronze.

1. Japan’s Currency of the Middle Ages

2.  This was used from 1336-1870 as the currency
 The Chinese character for mon is 文
 These coins were made in copper and iron, while
circulated alongside silver and gold ingots

3.  These coins were made with a hole in the middle so
that they could be strung together
 Through Japanese history, there were many different
styles of currency of many shapes, styles, designs, sizes
and materials, including gold, silver, bronze, etc.

4. 4000 mon = 16 shu = 4 bu = 1 ryo

5. http://en.wikipedia.org/wiki/Japanese_mon_(currency)