All except the 1964 as far as I can tell.. 65-67 were all Special Mint Sets so technically NO proofs were minted those years. Kinda like the Canadian Proof like issues. Sue me if I'm wrong. You'll get NOTHING! LOL
Coinfacts.com state that the Proof 1964 Kennedy Half $s were struck at the Philadelphia mint, thus no mint mark.
Proof Coins were all minted at Philadelphia up to 1964, afterwards they have been minted at Philly, West Point and San Francisco.