I have seen about a half dozen, counting the three misattributed on Wildwinds, two of which are cuirassed like yours, but not in as good condition.
Diocletian's contribution to Rome was great with his monetary reforms, building of the great baths and refurbishment of Curia Julia senate house. So I felt the need to purchase one of his coins, nowhere near as good as some of the coins in this thread, but still a reasonable example. Antoninianus minted Siscia 293-294 AD, 2.5 gm RIC V/11 263.
I just picked up one of my own! Diocletian AE Antoninianus, 24 mm, 4.16g. Obv: IMP CC VAL DIOCLETIANVS PF AVG., radiate, draped and cuirassed bust right Rev: IOV ET HERCV CONSER AVGG, Jupiter facing right, holding globe and sceptre, facing Hercules standing left, holding Victory on globe, club and lion's skin. B in lower center. Exergue: XXI. RIC V 323. (^^ I think so... That's what I was able to find.)
Ya, you have to watch out Justin pretty soon you'll be trying to get all the emperors portraits. Here's a Alexandrian Tet I picked up some time ago. Obviously after the OP coin but an older camera. I think I need to try and attempt better pics though.