Diocletian, Silvered AE21, 284-305 AD, Antioch Mint. 4.3gm 
  
Obv: IMP CC VAL DIOCLETIANVS PF AVG, Radiate, draped and cuirassed bust right 
Rev: CONCORDIA MILTVM, Emperor receiving Victory on globe

E Delta in lower centre, XXI in exergue  

RIC V-2 621 var (emperor)
Listed in RIC only for Maximianus and with dot preceding mintmark.

Unrecorded in RIC or any updated on-line reference with the 
E Delta field markings. Several other issues for Diocletian 
at Antioch list the E Delta / XXI mint mark, but not the 
Concordia Militvm issue. 
  
Contributed by Peter Dearing, October 2009