The Proof 1892 Indian Head Cent has a rather hefty mintage of 2,745, indicating a lot of collector interest at the time. Most of the examples known today have been well-preserved, thus PR64RB is the grade seen most frequently. The finish on the 1892 Proofs is brilliant and Cameo examples are a rare exception. Deep Cameo examples, if they even existed, would be exceedingly rare.
The key to buying Proof 1892 Cents (and any Proof Indian Head Cent) is to seek out coins with good color and problem-free surfaces. Spotted coins should be avoided or heavily discounted; conversely, coins with full red color or attractive toning deserve big premiums.