I have added quite a few coins of Diocletian to my collection recently and several are from his sole reign, before Maximianus was elevated to Augustus in A.D. 286. All the coins below were struck during his solo rule from A.D. 284- 285.

Diocletian
A.D. 285
AE Antoninianus 21x22mm 3.2g
IMP C C VAL DIOCLETIANVS P F AVG; Radiate, draped and cuirassed bust right, seen from rear.
PROVIDENTIA AVG; Providentia stg. l.; holding ears of corn and cornucopiae; at foot, modius; C to left.
RIC Vii Lugdunum 77; Bastien 14

Diocletian
A.D. 285
AE Antoninianus 21x22mm 3.2g
IMP DIOCLETIANVS AVG; Radiate, draped and cuirassed bust right, seen from the rear.
FELICITAS AVG; Felicitas standing left, holding caduceus and cornucopiae.
In ex. XXIB
RIC Vii Rome 157

Diocletian
A.D. 285
AE Antoninianus 22x23mm 3.4g
IMP DIOCLETIANVS AVG; Radiate, draped and cuirassed bust right, seen from the rear.
LAETITIA FVND; Laetitia, draped, standing left, holding wreath in right hand and rudder in left hand.
In ex. XXIZ
RIC Vii Rome 171

Diocletian
A.D. 285
AE Antoninianus 23mm 3.3g
IMP DIOCLETIANVS AVG; Radiate, draped and cuirassed bust right, seen from the rear.
MARTI PACIF; Mars standing to left, holding olive branch, spear and shield.
In ex. XXIE
RIC Vii Rome 173

Diocletian
A.D. 285
AE Antoninianus 23mm 4.5gm
IMP C C VAL DIOCLETIANVS PF AVG; radiate, draped and cuirassed bust right.
IOVI CONSERVAT; Jupiter standing left holding thunderbolt, small figure/ Diocletian to left.
In ex. QXXIT
RIC Vii Ticinum 220

Diocletian
A.D. 285
AE Antoninianus 21x22mm 3.5g
IMP C C VAL DIOCLETIANVS P F AVG; radiate and cuirassed bust right.
IOVI CONSERVAT; Jupiter standing left, leaning on sceptre and holding thunderbolt.
In ex. PXXIT
RIC Vii Ticinum 222

Diocletian
A.D. 284
AE Antoninianus 21mm 4.2g
IMP C C VAL DIOCLETIANVS P F AVG; Radiate, draped and cuirassed bust right.
VICTORIA AVG; emperor standing left holding globe and scepter, receiving wreath from Victory standing right; in center epsilon delta
In ex. XXI
RIC Vii Antioch 326

Diocletian
A.D. 284
AE Antoninianus 21mm 4.7g
IMP C C VAL DIOCLETIANVS P F AVG; radiate, draped & cuirassed bust right
IOVI CONSERVATORI AVG; Victory walking r., holding palm, presenting wreath to Diocletian stg. l., holding globe and sceptre; TR in center
in ex. XXI
RIC Vii Tripolis 330