When Q writes C_A, we all assume that missing I is symbol for the "Black Hat" version of CIA (for a whole host of reasons).
Could it be more than that?
How about:
C = Cleopatra
A = Akhenaten
Akhenaten was the first Pharaoh to change to a monotheistic religion that worships the "God of Light" symbolized by the sun disc.
Cleopatra was "The Last Pharaoh".
C_A would thus signify the pharaonic reign from Akhenaten through to Cleopatra (in reverse order of course).