The
in Imperial times is usually C; it is called the lunate sigma, because it's shaped like a new moon (BTW, it
still lives in Slavic alphabets, as in USSR being CCCP).
In front of the little boy's
head (and this is
Caracalla as
Caesar, not laureate, between 196 and 198) it says A N T
for Antôninos, the name
his father gave him to emphasize the claim to continuity with the Antonines.
Pat L.
P.S. I'm not sure, after all, that one can't see the ribbons of a
laurel wreath behind
his neck. You can see better.
P.P.S. Yes, as Luigi's example shows,
Caracalla as Augustus--and perhaps even with a
bit of beard.