Diocletian     22mm gVF antoninianus of Heraclea     Sear 3510     V.M. 21
IMP C C VAL DIOCLETIANVS AVG - Radiate, draped, and cuirassed bust right
CONCORDIA MILITVM - Jupiter standing l. offering Victory on a globe to Diocletian
Antoninianus minted in 292 - 294 AD, before the coinage reform of Diocletian.  ex. Ancient Auction House.

Diocletian    25mm VF follis of Rome   Sear 3534    V.M. 41   RIC 94a
IMP C DIOCLETIANVS P F AVG - Laureate head right
GENIO POPVLI ROMANI - Genius standing l. holding patera and cornucopia
Minted in 294 - 299 AD, this is a rather common coin but it demonstrates the radical change in the monetary system imposed by Diocletian.  ex. Ancient Treasures

Diocletian     27mm aVF/VF follis of Serdica     Sear 3543(v)     RIC 14a
DN DIOCLETIANO BAEATISSIMO SEN AVG - Laureated bust right wearing imperial mantle holding olive-branch and mappa
PROVIDENTIA DEORVM QVIES AVGG - Provendia and Queis standing facing
Abdication follis of Diocletian.  Nice symbolism on the reverse featuring Providentia (goddess of forethought) and Quies (goddess of rest).  Minted 305 - 306 AD.  ex. WCNC.