1964 D Kennedy Half Proof?

That's what I mean though the I matches the regular strike and the initials and rays match the proof

There are some 1964-P proofs that are known as a transitional variety which have the normal non-accented hair obverse, but the reverse with the broken rays and the FG same as Accented hair.

I also understand there are some business strikes (P and D) with the same reverse which matches the Accented Hair reverse, but again they do not have the Accented Hair obverse. This would explain your 1964-D business strike with the same reverse as Accented Hair P proofs.