Realcent.org

i know some of them are 40% silver but most arent
how can i tell them apart?

Go to Coinflation.com. All 40% are "S" mint. (However, all "S" mint are not 40%) The 40% weigh more. I think its 24 g for 40% and 22 g for clad.

beautiful thanks

Look at the edge, you can see the copper on the clad coins, the 40% one side will be bright nickel, other side duller silver color.

The 40% Ikes have the distinctive silver ring to them. I believe that each is .3161 oz of silver. As mentioned, the telltale sign is the S mintmark. The ones that are tarnished or hazy aren't good for more than bullion. Safe to experiment on those. If still in the cellophane and blue envelope or the brown proof holder that's another obvious sign. Sounds like that isn't the case here, though. Hope you have a bunch regardless.

1964 are 90% silver.

all 1965 to 1970 Halves are 40% silver.



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All 40% Ikes are S minted, but not all S mint Ikes are 40%

All 1971 and 1972 S mints are silver clad.
In 1973, 74, 76 S mints both silver clad and nickel clad were made.
All 1977 and 1978 S mints are nickel clad.