11. What does "twelve copper coins in the period of the Imperial Court" stand for?
"Kochosen" is the series of 12 copper coins issued in the 250-year period starting in 708, when Japan's first coin, the Wadokaihou, was issued.
The Court aimed at spreading the use of this series throughout the nation, which did not go smoothly.
When Japan entered the Heian Period, the economic situation deteriorated. The Court issued different coins successively in a short term, and designated their worth at 1 new coin being equivalent to 10 old coins. Due to a shortage of copper, the coins became small and inferior in quality.
Counterfeit coins were widely spread and issuing authority came to lose power.
After the series of Kochosen, coins were not to be issued for the next 600 years.
Actual coins from those days are exhibited on the second floor of the Mint Museum.