As silver prices continue to push for new 31-year highs and strive for an all-time record, silver coin values have blasted off for common coins once worth just 5, 10, 25 or 50 cents. It is difficult to imagine that a 50-cent piece with mintages in the tens of millions is worth nearly $17, or that a worn out nickel is valued at more than $2.50. But they are, thanks to silver prices that have jumped 172 percent since the end of 2009.Coins with 90 percent silver include dimes, quarters and half dollars that were minted before 1965. These...