? on my graded Ike from ANACS

I received my package from ANACS yesterday and cant figure out what something is on the label.
It says:
PR 67 Cameo
1974-S $ the cert #
PROOF CN
What does the CN mean?
Lori
It says:
PR 67 Cameo
1974-S $ the cert #
PROOF CN
What does the CN mean?
Lori
0
Comments
technically "cupro-nickel"
K S
Todd
800.954.0270