What do you think about this coin [решено]

To me the coin looks real. It is non magnetic 39.6mm 27.24 g. With the jewelry attachment it weighs a little more.
It is coin https://en.numista.com/catalogue/pieces15997.html

The patina looks like it is a silver coin.





It does have a strange mark that is stamped into the coin. It looks like "10"

Yup a real dollar that had the unfortunate end of becoming a piece of jewelry

Any idea what the 10 is that is stamped into the coin?

Probably a chop mark

http://coins.about.com/od/coinsglossaryc/g/Chop-Mark-A-Numismatic-Definition.htm