from Bern Sherman
The 1957-D Lincoln Cent is a very common coin except in grades above MS66. Thousands of 1957-D Cents have been submitted to PCGS in an attempt to achieve the coveted MS67RD grade. As a result, the population of Red 1957-D Cents is swollen, while the populations of Red-Brown and Brown examples are low. This does not mean that Brown and Red-Brown examples are scarce; instead, it means that their value is too low to justify having them graded.
Inspect all examples for carbon spotting. The most desirable examples are as spot-free and as fully-struck as possible and they will exhibit full, blazing red color.