If your coin says "QUARTER DOLLAR" on the back it's a Washington quarter and is worth only 25¢ John F. Kennedy lived in the 20th century and would not be wearing a powdered wig!
If your coin says "HALF DOLLAR" on the back it's a halfdollar and is worth extra for its silver content. There's more information at the Related Question.
1965 to 1969 Kennedy half dollars were all struck in 40% silver and have a bullion value of about $2.00
25 cents
Twenty five cents
Pre-1965 US quarters are 90% silver with a value of about $2.50 just for the silver.
No, only Kennedy Half dollars from 1965-1969 had any silver in them, but that's 40% not 90%.
1965 to 1969 Kennedy half dollars were all struck in 40% silver and have a bullion value of about $2.00
25 cents.
25 cents
It's worth 25 cents.
Twenty five cents
Pre-1965 US quarters are 90% silver with a value of about $2.50 just for the silver.
No, only Kennedy Half dollars from 1965-1969 had any silver in them, but that's 40% not 90%.
As of 22 January 2014, the melt value of a U.S. silver quarter (dated before 1965) is $3.58.
The coins are face value and have no silver.
There are no mintmarks on 1965 Kennedy half dollars.
So many were made the coin is face value just spent it.
Please post a new, separate question. JFK is on the US half dollar. George Washington is on the US quarter.