1964-D LMC Wrong Mint Mark Punch?

Probably a lightly punched die.

That is a bizzard looking D, it doesn't even look like a real MM.

This is a case of a combination of things to differing degrees.

1. Lightly punched die.
2. Simple die wear.
3. Die polishing that raised the base of the D making it thinner.

#3 is the most likely culprit here because mintmarks have beveled relief..they are thinner as you come up off the field. If the field is raised from beneath the mintmark, it will get thinner as you go up.

Imagine it like this...take the great pyramid and look at it from above. As you bury it in sand, it appears smaller around as you bury it. Same thing with polishing the ground away from under the mitmark.

It maybe weak but just looks odd for 1964-D cent mint mark. plus its the year the coin presses never shut down they made more coins that year than they make in 4 prior years