The 1883 Half Dollar is a great date because of its miniscule mintage of only 8,000 coins. However, it is a tough coin to find in any condition, thus many collectors resort to a Proof version (which is twice as plentiful as the Mint State edition). To compund the problem, there are many examples that are so Prooflike that they are often confused with Proofs. On the other hand, there is a tendency to designate Proofs as Mint State because of the higher value of the latter.
The typical Mint State 1883 Half Dollar grades out at MS64. The very best coins are MS67 or better, with the finest example being a single PCGS MS67+.