I'll give it a RD-64, only because of the bottom of the stairs are missing, which also leads to the keys in the left center of the memorial being weakly struck too ...
I'd give it a 66RD. My understanding is that the grade is partially determined by how well the coin is struck by the die. If the bottom of the stairs aren't on the die they won't appear on the coin, but the coin captured all there was to capture.
Looks like a 65 to me. I just can't get past the bottom of the T in CENT. But help me out guys; stars? What stars?
66 is my guess as well. It's obviously a very Gem coin but the flaws and strike on the reverse could have kept it in a 65 holder. It had a long shot of making 67 since the luster is so great. It is "obviously" a mint set coin.