Constantine I AE follis, Constantinople. AD 307-337. 
28mm, 3.11 g. 

CONSTANTINVS MAX AVG, laureate head right.
SPES PVBLICA, standard with three dots on drapery, chi-rho above, serpent below. A in left field.

Mintmark CONS.
RIC VII 19; Sear 16287. 

Very rare.
With permission of cngcoins.com, Triton XIV, lot 835. Jan. 2011.