Agree with the above. And a glob of glue on the reverse that held it in somebody's coin book. Once a coin has experienced this much wear and tear any potential error becomes somewhat moot. Nice Buffalo though. Enjoy it!
It was part of a jewelry piece and slightly dished to fit its purpose. That "glue" may be silver solder on the reverse. Many people made nickel bracelets in the '60s and '70s and I'd be willing to bet this was part of one. All of the coin is consistent with that scenario as the reverse is still in better condition with the tail and most of the horn showing, while the obverse is worn smooth, which would occur on a bracelet.
