From what I found during a very brief look at the internet, 1864 is the year the mint shifted from a copper-nickel alloy to bronze for cents. There are three varieties: copper-nickel, bronze, and bronze with the letter "L" on a ribbon trailing from the back of the headdress. The values are least: bronze, next: copper-nickel, most: bronze with "L". The coin in this post is defaced and would have little or no value to a coin collector.
With respect to the coin in this post, the hole in the center is small and not circular making it less than ideal for wearing on a string. It looks more like it may have been used as a pommel on a home-made knife except that it doesn't appear as if it has had a tang peened or bent across it to hold a grip in place. In any case, it has been severely altered for some reason but I doubt jewelry or identification were it. Maybe a button? Maybe as ethnic decoration to clothing?