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.
silver
If the portrait looks like JFK it's a JFK half dollar! More specifically, if it's dated 1964 or later.
It isn't. No 1969 quarters are silver. Silver quarters were only made in 1964 and before. All quarters from 1965-present are copper-nickel. There isn't even a 1969 commemorative quarter that was struck in silver. There is no possible way for it to be silver.
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.
1964 is an extremely common date for Kennedy halves, but the coins are 90% silver. At present, one is worth about $10.
The coin is only 40% silver and has a value of $2.73 only the 1964 Kennedy half dollar was 90% silver.