Arthrene, I thought you might like to see the resource that I use to identify my Japanese coins. Please excuse the horrible calligraphy, but I think the characters are recognizable enough that you might be able to give dating Japanese numismatics a go. :)
There's also a neat page on lioncoins.com that can help. Once you get the basics down, it's really pretty easy.
http://www.lioncoins.com/nippon.htmImage:
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