So is speeding. There might be some crazy radiation related super science way to determine if a lump of silver came from a specific collection of coins, but once it's melted down, and the impurities driven out, silver is silver and you can't really tell that it came from coins.
No, not in general anyways. There are specific regulations on smelting pennies and nickels (and it's specifically nickels, not half dimes).
So you can smelt any silver coins minted by the US except for the WW2 silver nickel.
So is speeding. There might be some crazy radiation related super science way to determine if a lump of silver came from a specific collection of coins, but once it's melted down, and the impurities driven out, silver is silver and you can't really tell that it came from coins.