Caracalla, AE30 of Philadelphia, Lydia. 198-217 AD.

AYT K M AYR ANTWNEINOC, laureate, draped, cuirassed bust right, seen from the back.
EPI CTRA IOYLIANOY A POL FILADELFEWN, coiled serpent
with head raised left and protruding tongue, on the back
of a bridled horse pacing left.

BMC 85; Kraft pl. 74, 5b (same dies). 

With permission of Ken Steiglitz, Sept. 2013.