Robert Draper's fascinating story about Donald Rumsfeld in GQ is the worth the luxurious read. The highlight is his discovery that Rumsfeld, not particularly a pious man, interspersed biblical references with classified daily briefings in order to prompt a more friendly contextualization of the war from the perspective of those who were commanding it.
The briefings are replete with bodacious classification markings, like TOP SECRET//HCS-COMINT-GAMMA//ORCON, NOFORN//EXDIS/X1, X6.
TOP SECRET -- well, you know what that means. It's the formal "classification" of the document.
HCS-COMINT-GAMMA -- This is the SCI control system phrase, with "SCI" being the catch-all term for a variety of Sensitive Compartmented Intelligence.
HCS refers to the "Humint Control System," which is a special classified information distribution channel for intelligence received from human sources or obtained by covert HUMan INTelligence case officers working around the globe. Because of the sensitivity of the sourcing, all info marked HCS must be laundered through this special security channel. COMINT -- information derived from signals intelligence collection platforms. GAMMA is a subcompartment of COMINT.
ORCON -- Stands for "Originator Control," which gives the office which has classified the briefing the control over its dissemination.
NOFORN -- Don't show this to foreign governments!!!
EXDIS -- The distribution is limited to an "EXclusive" number of people. Note that the briefing slide contains a marking that shows there to be only ten copies of the briefing in existence.
X1, X6 -- These are exemption codes; generally, classified information is releasable or declassifiable after 10 years; this coding system gives the military and government a series of exemptions to extend that period. X1 refers to information about collection platforms, like secret spy satellites, hidden bugs or other sensitive programs. X6 refers to information that might damage the relationship between the U.S. and other governments.
Several of the GQ slides have blacked out some portion of the classification line. That's because the classifications themselves remain a secret, probably because they refer to sub-channels of classified information that are specific to ongoing operations.