Caracalla AE13 provincial of Markianopolis. 
Obverse:  Bust of a young Caracalla, laureate, facing right.  (A)NTONI(NOS).

Reverse:  (MAR)KIANOPOLE(ITON), A serpent climbing right leg of a tripod altar. 
   The "sipping serpent" is a reference to Hygieia, the 
  Greek counterpart of the Roman Salus.

References:  Not in Sear Greek Imperials or SNGCop.

From the Dave Surber collection.  
Obtained from a junk box for $5 at a coin show in 1998.