Nice find. I've nabbed a few of those from junk boxes. You can't tell its silver from looking at it because its only 30%, so a lot of them slip by dealers.
And he that hath lyberte ought to kepe hit wel / For nothyng is better than lyberte / For lyberte shold not be wel sold for alle the gold and syluer of all the world. -Caxton's edition of Aesop's Fables, 1484
Depends on the coin type and the denomination. Mexico has had quite a few different coin regimes over the last 100 years.
We are talking about this coin:
And he that hath lyberte ought to kepe hit wel / For nothyng is better than lyberte / For lyberte shold not be wel sold for alle the gold and syluer of all the world. -Caxton's edition of Aesop's Fables, 1484