The texture of the frosting determines the Proof, Cameo and D-Cam grades.


Look closer at the frosting as they increase as the grade progresses from Proof, Cameo and D-Cam.
There are more of these than the pre 1970 coins as the frost on the earlier proof only lasted 100 strikes before it was worn off the die. The post 1971 coins had a different method and it seemed they touched up the dies more often. Today it is done with lasers:

