The 1967 Uncirculated Kennedy Half Dollar does not contain a mint mark. The Mint intentionally left mint marks off coins produced between 1965-1967 to prevent coin hoarding. Kennedy Half Dollars stuck from 1965-1970 were composed of Silver and Clad content. The 1967 Kennedy Half Dollar has the largest mintage from all Uncirculated Kennedy Half Dollars produced from 1965 to 1970.
It is very common in all circulated grades all the way up to MS63 condition more or less. In MS64 to MS65 it starts to become a little more scarce but still easily obtainable with most examples being raw or uncertified. In MS66 the coin now becomes very challenging to acquire with possibly a few hundred examples available and the odds are you won't find one in circulation, rolls or even bags. Most examples have probably already been graded. In MS67 it is extremely scarce with about a dozen known and none being finer.