You don't.
Not all silver. It is referred to as silver clad. Silver on both sides (40% by weight) with copper in the center. The semi-solid silver Kennedy half dollar stopped production in 1964, made of 90% silver. See the related link for more information.
All 1964 JFK halves were struck in an alloy of 90% silver and 10% copper. 1964 was the only year for that composition. 1965-70 halves were struck in a 40%-silver clad composition. All circulating halves dated 1971 and later have no silver; they're made of the same copper-nickel "sandwich" metal used for dimes and quarters.
No 1977 halves were struck in silver. It's also very difficult to tell by a coin's ring because clad coins are frequently irregular internally due to thickness differences that occur as the clad stock is rolled out. Look at the coin's edge. If it's copper-colored like the edge of a quarter or dime, you have an ordinary copper-nickel circulation half that's worth face value.
A 1964 dime is made of 90% silver and 10% copper, known as a "silver dime" because of its silver content. These dimes were the last to be minted with silver before the composition changed to a copper-nickel alloy in 1965.
John F. Kennedy 50 cent pieces feature a portrait of JFK on the obverse side of the coin. The coin was minted between 1964 and 2021. It should also have the words "Liberty," "In God We Trust," and the mint mark on the coin.
The 1964 Kennedy half has .36169oz of pure silver in it.
About $6 for its silver content
The 1964 Kennedy half dollar contain 11.25 grams of silver. Kennedy half dollars from 1965 through 1970 contain 4.60 grams of silver.
1964 was the only year JFK halves were made of 90% silver alloy. The composition was changed to 40% silver clad in 1965, and to copper-nickel clad in 1971. A 1964 Kennedy Half Dollar contains .3617 ounces of pure silver. Multiply this by the spot price of silver to get the bullion value of the coin. At the time of this writing, silver was $16 an ounce, making a 1964 Kennedy Half Dollar worth about $5.80
About 10.25 grams.
1964 Kennedy halves are the most common 90% silver half dollars. Most are valued just for the silver, about $12.00.
The actual amount of pure silver is .36169 of an ounce.
Please, turn the coin over and look at the denomination on the back. It's a HALF dollar, not a dollar. The 1964 Kennedy half is a 90% silver coin, but very common. The value would be only for the silver, about $15.00 as of 9-1-11.
The Kennedy Half Dollar was first minted 1964, in 90% silver.
The U.S. Mint did not issue any .999 silver Kennedy coins in 1964.
The coin is only 40% silver and has a value of $2.73 only the 1964 Kennedy half dollar was 90% silver.
1964 is an extremely common date for Kennedy halves, but the coins are 90% silver. At present, one is worth about $10.