Kevin sent us a picture of a Japanese 10 yen coin. These were minted in bronze from 1951 to 1989. These coins weigh 4.5 grams and are 23.5mm in diameter. A few of these coins have higher catalog values than the rest; a look at recent auctions shows that these values are not indicative of prices realized in the current market, which are much lower. The ones with higher catalog values are listed below. The rest are worth face value: 10 yen in Japan, about 9 US cents. If you have one of the dates not listed below in fully uncirculated condition, a collector will probably pay a few US dollars to add it to his or her collection.
There is a good date converter at DateConverter.net. Better dates (catalog values are for fully uncirculated coins only):
1951: $150 (U.S. dollars)
As mentioned above, please keep in mind that these values are catalog values and are often different from actual buy and sell values. For more information on catalog values, please check out our Terminology page.