Need Help Identifying Cam Designation On 1950-S Era Wheat Cents

I have 42 1955-58 Proof Wheat Cents. I have been trying to sort them and figure out my best ones. One of the things that is really confusing me is the CAM designation. On modern coins you have the frosty look which makes it obvious, but that doesn't seem to apply with these older cents.

I have looked at quite a few on auction sites but still can't really figure out the difference. Do you guys know how to tell the difference between regular 1950s era proof cents and Cameo ones? Thanks!

Here is an average example




Here is a spread of a few of them in high light just to help give an idea of some of the coins.