The coin I found is a 1/2 sen from Japan. The time period is Meiji 10-25 , the years minted 1868-1912. The Internet has some good pictures listed. I did clean the coin, found out it was made from copper and the diameter is 22mm,one side of the coin is in pretty ruff shape. I guess I'll will never know how the coin ended up in our back yard . Happy Holidays Jim