This is the first year in which the Mint struck Proof Lincoln cents with a Memorial reverse design. Most coins came in nice condition ranging from PR63 to PR65 quality. Most of the nicer coins above grade PR65 were more than likely cherry picked from Proof Sets and submitted to get graded since coins of PR66 quality coins and higher command a premium over the entire Proof Set itself.
In grades of PR67, they are hardly encountered and most of these coins have already been removed from Proof Sets. In PR68 condition they are now considered scarce and there is strong competition by collectors to try to find them in this condition or higher. In PR69 condition, they are very scarce and this is the highest condition that someone can currently find since PCGS has not graded any examples higher than PR69.