I'm going to assume the "weird marks behind the head" in the first pic are just an odd lighting effect and not actual marks on the coin, as I can't see them in the second pic. I'm not entirely sure what a "Sheldon sleeve" is, but it seems to have done an okay job of preserving this coin.
The coin is certainly Uncirculated - which is not all that unusual for 1964-dated pennies, since many were kept as souvenirs of the old money once 1966 rolled around.
I am seeing a hint of a fingerprint on the reverse beneath the kangaroo, unless it's that same lighting glitch; it worries me enough to shy away from a Gem Unc grade. Perhaps MS-63 or 64, on the American standard?
Edit: I made my post without reading Sel's post. I'm glad we seem to agree on the grading.

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