Final answer:
The exterior packaging must be stamped/marked as Controlled Cryptographic Item (CCI) for it to be considered CCI Communication security (COMSEC) serialized control.
Step-by-step explanation:
The property that is considered CCI Communication security (COMSEC) serialized control and must be stamped/marked 'Controlled Cryptographic Item' or 'CCI' is the Exterior Packaging.