Diocletian Emperor of the Roman Empire from 284 to 305.
Gaius Aurelius Valerius Diocletianus Augustus, born Diocles, was Roman emperor from 284 to 305.

Born to a family of low status in the Roman province of Dalmatia, Diocletian rose through the ranks of the military to become cavalry commander to the Emperor Carus. After the deaths of Carus and his son Numerian on campaign in Persia, Diocletian was proclaimed emperor. The title was also claimed by Carus' other surviving son, Carinus, but Diocletian defeated him in the Battle of the Margus.

Diocletian's reign stabilized the empire and marks the end of the Crisis of the Third Century. He appointed fellow officer Maximian as Augustus, co-emperor, in 286.

He reigned twenty-one years and then abdicated voluntarily. He lived out his retirement in his palace on the Dalmatian coast, tending to his vegetable gardens.
Diocletian
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An BL Tetradrachm struck 284-285 AD in Alexandria
Obverse: laureate, draped bust right; A K Γ OYAΛ ΔIOKΛHTIANOC CEB

Reverse: Elpis standing left, holding flower and raising skirt; LA

Diameter: 19 mm
Die Orientation: -
Weight: 7.12 g
Nov 284 - 28 Aug 285 AD
Milne 4750; Curtis 1980; Geissen 3202; SNG Cop 968; Emmett 4046; BMC Alexandria p. 323, 2499 var
/Files/Images/Coinsite/CoinDB/Diokletianus_Alexandria_Homonoia_LB.jpg
An BL Tetradrachm struck 285-286 AD in Alexandria
Obverse: laureate and cuirassed bust right; A K Γ OYAΛ ΔIOKΛHTIANOC CEB

Reverse: Dikaiosyne (Aequitas) standing half left, holding scales and cornucopia; L_B

Diameter: -
Die Orientation: -
Weight: 7.3 g
29 Aug 285 - 28 Aug 286 AD
Milne 4770; Curtis 1967; Dattari 5645; SNG Cop 978
/Files/Images/Coinsite/CoinDB/Diokletianus_Alexandria_Zeus_LZ.jpg
An BL Tetradrachm struck 290-291 AD in Alexandria
Obverse: laureate head right ΔIOKΛHTI_ANOC CEB

Reverse: Zeus standing half left, wearing chalmys, holding patera and scepter. eagle at feet; L_Z

Diameter: -
Die Orientation: -
Weight: 8.2 g
29 Aug 290 - 28 Aug 291 AD
Milne 4946; Curtis 2045; BMC Alexandria p. 321, 2475; Geissen 3250; Kampmann 119.68; Emmett 4087
/Files/Images/Coinsite/CoinDB/DiocletianLargeFollis-2.jpg
An AE Follis struck 297-298 AD in Heraclea
Obverse: IMP C C VAL DIOCLETIAN P F AVG, Laureate bust right

Reverse: GENIO POPVLI ROMANI, Genius standing left, holding patera and cornucopia

Diameter: 0 mm
Die Orientation: 0 H
Weight: 0 g
No notes for this coin
RIC VI 19a
(5) Diocletian
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An BL Antoninianus struck an unknown year in Ticinum
Obverse: IMP C VAL DIOCLETIANVS AVG, cuir. bust with rad. head right

Reverse: HERCVLI CONSERVAT, Hercules standing right, holding lion-skin

Diameter: 0 mm
Die Orientation: 0 H
Weight: 3.1 g
No notes for this coin
No references provided for this coin
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An AE unit struck 303 A.D. in Carthage
Obverse: MP C DIOCLETIANVS PF AVG, radiate, draped and cuirassed bust right.

Reverse: VOT-XX-FK in three lines within wreath. (FK is the mintmark).

Diameter: 20 mm
Die Orientation: 0 H
Weight: 2.2 g
No notes for this coin
Carthage RIC VI 37a
(7) Diocletian
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An AE Antoninianus struck 285 A.D. in Ticinum
Obverse: IMP CC VAL DIOCLETIANVS PF AVG., radiate, draped and cuirassed bust right

Reverse: MARS VICTOR, Mars walking left, holding spear and trophy. Mintmark VIXXIT

Diameter: 22 mm
Die Orientation: -
Weight: 3.11 g
No notes for this coin
RIC V239
(8) Diocletian
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An AE Antoninianus struck 288 A.D. in Ticinum
Obverse: IMP C VAL DIOCLETIANVS AVG, radiate cuirassed bust right

Reverse: IOVI CONSERVAT, Jupiter standing left, holding thunderbolt and sceptre.

Diameter: 21.26 mm
Die Orientation: -
Weight: 2.8 g
mintmark: PXXIT
RIC V 225
/Files/Images/Coinsite/CoinDB/1295_Diocletian.JPG
An AE Post-reform Radiate struck c. 295-299 AD in Cyzicus
Obverse: radiate, draped and cuirassed bust right; IMP C C VAL DIOCLETIANVS P F AVG

Reverse: Diocletian standing right, holding parazonium, receiving Victory on globe from Jupiter standing left holding long scepter; CONCORDIA MI_LITVM / KΓ

Diameter: -
Die Orientation: -
Weight: 3 g
No notes for this coin
RIC VI Cyzicus 16a
/Files/Images/Coinsite/CoinDB/127_Diocletian_Cyzicus.jpg
An AE Follis struck 297-299 AD in Cyzicus
Obverse: laureate head right; IMP C C VAL DIOCLETIANVS P F AVG

Reverse: Genius standing left, pouring out patera and holding cornucopia; GENIO POPV_LI ROMANI / KΓ

Diameter: 27 mm
Die Orientation: -
Weight: 9.66 g
No notes for this coin
RIC VI Cyzicus 12a
(11) Diocletian
/Files/Images/Coinsite/CoinDB/388_Diocletian.jpg
An AE Antoninianus struck 285-286 AD in Rome
Obverse: radiate and cuirassed bust right; IMP DIOCLE_TIANVS AVG

Reverse: Jupiter standing half left, wearing chalmys, holding thunderbolt and long scepter; IOVI CONSER_VAT AVGG / XXIΓ

Diameter: -
Die Orientation: -
Weight: 3.59 g
No notes for this coin
RIC V-2 162 Rome
(12) Diocletian
/Files/Images/Coinsite/CoinDB/870_Diocletian_Tripolis.jpg
An BL Antoninianus struck 284 AD in Tripolis
Obverse: radiate, draped and cuirassed bust right; IMP C C VAL DIOCLETIANVS P F AVG

Reverse: Diocletian right receiving Victory on globe, holding parazonium; Jupiter left giving Victory on globe, holding long scepter; IOVI CONSERVATOR_I AVG / TR / XXI•

Diameter: 24 mm
Die Orientation: -
Weight: 3.75 g
ex Gitbud and Naumann
RIC V 328
/Files/Images/Coinsite/CoinDB/Diocletian_Providentia_Deorum_PLG.jpg
An AE Follis struck 305-307 AD in Lugdunum
Obverse: laureate bust right wearing imperial mantle, holding olive branch and mappa; D N DIOCLETIANO BEATISSIMO SEN AVG

Reverse: Quies standing left extending hand against Providentia who is holding scepter and branch; PROVIDENTIA DEORVM QVIES AVGG / T_F / PLG

Diameter: -
Die Orientation: -
Weight: 9 g
305 - early 307 AD
RIC VI 200a var. (obv. legend-BAEATISSIMO)
/Files/Images/Coinsite/CoinDB/Diocletian_-_argenteus(1).jpg
An AR Argenteus struck 294 AD in Rome
Obverse: laureate head right; DIOCLETI_ANVS AVG

Reverse: tetrarchs wearing military dress, sacrificing over tripod in front of turreted enclosure with gate; VIRTVS__MILITVM / A

Diameter: -
Die Orientation: -
Weight: 1.96 g
No notes for this coin
RIC VI 40a; RSC 516g
/Files/Images/Coinsite/CoinDB/Diocletian_(Obv_and_Rev).jpg
An AE Follis struck c. AD 296-303 in Londinium
Obverse: IMP C DIOCLETIANVS P F AVG, laureate and cuirassed bust right

Reverse: GENIO POPV-LI ROMANI, Genius standing left, holding patera and cornucopiae

Diameter: 26 mm
Die Orientation: 7 H
Weight: 9.14 g
No notes for this coin
CT 2.01.003 (10); RIC 6a & 16A; cf. Sear 12760; S 696
/Files/Images/Coinsite/CoinDB/419_Diocletian_Trier.jpg
An BL Follis struck 298-299 AD in Treveri
Obverse: laureate, cuirassed bust right; IMP DIOCLETIANVS P AVG

Reverse: Genius standing left, holding patera and cornucopia, modius on head, chalmys over shoulder; GENIO POPV_LI ROMANI / A _ * / TR

Diameter: 0 mm
Die Orientation: 0 H
Weight: 8.72 g
No notes for this coin
RIC VI Trier 292a
(17) Diocletian
/Files/Images/Coinsite/CoinDB/769_Diocletian_Cyzicus.jpg
An AE Antoninianus struck 285-293 AD in Cyzicus
Obverse: radiate, draped and cuirassed bust right from behind; IMP C C VAL DIOCLETIANVS AVG

Reverse: Diocletian standing right, holding parazonium, receiving Victory on globe from Jupiter standing left, holding Victory on globe and long scepter; CONCORDIA MILITVM • / B / XXI•

Diameter: -
Die Orientation: -
Weight: 3.4 g
clipped
RIC V-2 306
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An AE Follis struck 297-298 AD in Heraclea
Obverse: IMP C C VAL DIOCLETIANVS P F AVG, Head of Diocletian facing right, wearing laurel wreath

Reverse: GENIO POPVLI ROMANI, Genius standing facing left, pouring libation from patera and holding cornucopia; HTB in exergue

Diameter: 29 mm
Die Orientation: 12 H
Weight: 9.29 g
No notes for this coin
RIC VI Heraclea 19a
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An AR Argenteus struck an unknown year in Rome
Obverse: DIOCLETIANVS AVG, laureate bust right

Reverse: PROVIDENTIAE AVGG, the four Tetrarchs (Diocletian, Maximianus, Galerius and Constantius) sacrificing over tripod before campgate with six turrets

Diameter: 17 mm
Die Orientation: -
Weight: 2.8 g
No notes for this coin
RIC VI 10a
/Files/Images/Coinsite/CoinDB/Diocletian_(Obv_and_Rev)(0).jpg
An AE Follis struck c. AD 303-5 in Londinium
Obverse: IMP DIOCLETIANVS P F AVG, laureate, draped and cuirassed bust right, seen from behind

Reverse: GENIO POPV-LI ROMANI, Genius standing left, holding patera and cornucopiae

Diameter: 27 mm
Die Orientation: 7 H
Weight: 9.31 g
This is a rarer bust type for Diocletian. Also, the pellet between the feet on the Genius does not appear to be a common feature on these earlier coins. I contacted Lee Toone and he has said that it is probably a guide mark for engravers but may be something else.
CT 3.01.003; RIC 10/24 cor.
/Files/Images/Coinsite/CoinDB/Diocletian(2).jpg
An AE Antoninianus struck 285 AD in Ticinum
Obverse: IMP CC VAL DIOCLETIANVS PF AVG / radiate, cuirassed bust right

Reverse: IOVI CONSERVAT / Jupiter standing left, holding thunderbolt and sceptre

Diameter: -
Die Orientation: -
Weight: 3.4 g
No notes for this coin
RIC V 222
/Files/Images/Coinsite/CoinDB/Diocletian_(Obv_and_Rev)(1).jpg
An AE Follis struck c. AD 296-303 in Londinium
Obverse: IMP C DIOCLETIANVS P F AVG, laureate and cuirassed bust right

Reverse: GENIO POPVLI ROMANI, Genius standing left, holding patera and corncopiae

Diameter: 29 mm
Die Orientation: 6 H
Weight: 10.38 g

A very unusual style of bust on this wonderful medallic coin from the London mint. After consulting with Lee Toone i'm going with CT 2.01.003 (8), but there are so many subtle variations in style during this period. "A fine example of this coarser style probably engraved by an Allectan engraver learning how to adapt to the larger canvas of the new (for Britannia) nummi" (Lee Toone - 20.07.20) Ex. Brian Henry Grover Collection (Roma Numismatics E-Sale 72; Lot 1394)

CT 2.01.003 (8); RIC 6a & 16a; S 696