The values depend very much on the coins' dates.
1963 and 1964 halves are 90% silver and are worth at least $6-$7 retail as of 06/2010.
1965-68 are 40% silver and are worth at least $3.50
No 1963 Kennedy half dollars exist. 1963 is the last year of the Franklin half dollar. 1964 is the first year for Kennedy.
1963 is a common date for half dollars and the value is primarily for the coin's silver content. At present, it's worth around $11.
If it shows any wear at all the value is about $6.00 just for the silver. All Franklin half dollars (1948-1963) are considered common.
So many 1968 Kennedy half dollars were made and saved the value is just for the silver, about $6.00
So many were struck, if it shows any wear the value is for the silver, about $11.00.
In 1968 the Kennedy half dollars were still struck in 40% silver so it has the silver value only, about $2.50. The gold plating was NOT done at the Mint and adds nothing to the value.
20 half dollars have a face value of a $10.
So many were struck, if it shows any wear the value is for the silver, about $11.00.
Franklin half dollars (1948-1963) are not rare or even scarce so if the coin has any wear at all, value is just for the silver about $11.00.
All US half dollars minted from 1948 to 1963 are called Franklin halves because they carry a picture of Benjamin Franklin. There's more at the Related Question.
No US silver dollars were made after 1935, look at the back of the coin for 'Half Dollar'.
5-3-11>> If it shows any wear at all the value is about $15.00 just for the silver. All Franklin half dollars (1948-1963) are considered common.