1965-1970 Kennedy Half Dollar
From 1965 to 1970, Kennedy Half Dollars were 40% silver, and they did not have a mint mark. The mint mark location changed in 1968, moving from the reverse (below the eagle's claw on the 1964 coins) to the obverse (below Kennedy's neck and above the date). The Philadelphia Mint coins (1965-1970) do not have a mint mark, while coins from the Denver (D) and San Francisco (S) Mints do.