Caracalla AR Denarius. 206 AD. 

ANTONINVS PIVS AVG, laureate head right
PONTIF TRP VIIII COS II, Mars in military dress standing 
right, leaning on shield holding reversed spear. 

RIC IV-1, 83; RSC 424. 

Sold by "kernunnos" on ebay for $26.87 on 15th Aug. 1999.