what is the difference is grading between these two, that makes the value over $2000 difference? I guess my question is what is DCAM compared to cameo, and are that that much more rare? thanks!

You can look at it like a cake.

The more frosting the richer it is.

...Tony...

That's pretty much it. Really hard to find a lot of the Kennedy's in CAM, let alone DCAM.

I check through about 15-20 pre-72 proof sets today, not one Kennedy was even close to the CAM designation.

I'm not a follower of this but there was a lot of discussion in the past about the depth of the mirror effect to indicate DCAM - Deep Cameo vs just Cameo. Of course the frosting must be even and complete for either designation.

it should be obvious looking at the first photo , that there is a lack of frosting on a large chunk of Kennedy's cheek and temple.

I think the cameo and DCAM designation is even more rare for the SMS halves. I was just looking at the Kennedy in my 67 set the other day and it's common mirrored devices.

My understanding is that it is the depth of the mirrors and the heaviness of the frost and the resulting contrast between the two. Of course, the relative value is also going to depend upon the piece of plastic it is in.