While the Japanese currency may fall a bit, he said, there will not be much movement.
The dollar gained about half a yen against the Japanese currency.
Generally positive sentiment about the dollar also helped it advance against the Japanese currency.
The sales were viewed as an effort to curb further erosion in the Japanese currency.
A 1.1 percent fall against the Japanese currency left the dollar at 104.23 yen.
The mint made coins which are recognized as the first Japanese currency.
It fell more than a yen against the Japanese currency.
Japanese currency has a history covering the period from the 8th century to the present.
It attributed the decline to tough competition in key markets and the strong Japanese currency.
The dollar fell to 140.70, its lowest level against the Japanese currency in decades.