Is it possible to identify this Roman coin ?

I think it is a Roman coin but no idea what it is. Diameter is about 28mm. Can anyone identify it for me please  ?

Thanks.

Diocletian antoninianus. 284-305 AD.  You can see in the legend above his head “DIOC"

The rest of the legend isn't readable. It's similar to this type. 

 Obverse lettering - looks like 

IMP C C VAL DIOCLETIANVS P F AVG 

Many thanks both😃, just the answer I was looking for.

Cheers.

 On the reverse - just above the figure on the right, 

looks like an  I  letter, so could be 

CONCORDIA MILITVM 

 as the lettering on the right looks vaguely like TVM there. 

 Example, of design, but not 28mm > 

N#306119  [21.5 mm]