Errors

A brockage occurs when the coin gets stuck to the die and the next strike produces a mirror image on one side of the planchet. These are fairly common; though reverse brockages are rarer than obverse, because the mint worker could more easily see if the planchet was stuck to the obverse die.
This is a reverse brockage for Gallienus (A.D. 260- 268) The reverse is AETERNITAS AVG, Saturn with harpa standing right; PXV in exergue. RIC 606
obverse brockage Tetricus I 271-274 17mm 2.3g
Partial reverse brockage Constantine I A.D. 320 18x19mm 2.3g CONST-[ANTINVS AVG]; helmeted and cuirassed bust right. VIRTVS EXERCIT, [Valor of the army] Standard inscribed VOT/XX with captive seated on ground on either side, S-F across fields. in ex. AQ[P] RIC VII Aquileia 48
Obverse brockage Constantine I A.D. 320 17mm 3.6g CONS-TANTINVS AVG; high crested helmet (bowl shaped) and cuirassed bust right. For reverse see-- VICTORIAE LAET PRINC PERP; two Victories stg., facing one another, together holding shield inscribed VOT PR on altar. in ex. P [2 captives] L RIC VII Lyons 79
Obverse brockage Constantine I 19x20 3.0 SOLI INVICTO COMITI Rome
obverse brockage Constantine I 20x21mm 3.3g IOVI CONSERVATORI Siscia
Obverse brockage Constantine I A.D. 318- 320 20x21mm 3.2g Siscia mint should have been VICT[ORIAE] LAETAE PRINC PERP reverse
This Constantine I brockage has a line under the reverse bust. For some obscure reason, somebody did this to the flan before striking; which is why the bust obscures most of it. 21mm 2.9g IMP CONSTANTINVS P F AVG
Constantinopolis brockage from Trier 15mm 1.8g Ex 1989 Nether Compton (Dorset) Hoard
Helena AD 324-330 Æ Follis 13mm 1.5g Obverse brockage
Obverse brockage Constantius II 16mm 1.7g
A double strike occurs when the hammer "bounces" which allows the coin flan to move in between strikes. These double strikes can vary from barely discernible to coins that have complete 180 degree rotation.
This Aurelian was struck and then flipped 180 and struck again. Aurelian A.D. 270- 275 IMP C AVRELIANVS AVG; radiate & cuirassed bust left. SOLI INVICTO•; Sol stg. left, right hand raised, left holding globe, at foot captive; ✶ in left field . In ex. KA RIC Vi Tripolis 390
Maximianus A.D. 285- 286 Æ Antoninianus 23mm 3.1g IMP MAXIMIANVS P F AVG; radiate, draped and cuirassed bust right. IOVI CONSERVAT AVGG; Jupiter standing left, leaning on sceptre and holding thunderbolt. In ex. XXIT RIC Vii Rome 506
Constantine I A.D. 314- 315 21mm 3.7g IMP CONSTANTINVS P F AVG; laureate, draped and cuirassed bust right. SOLI INVIC-TO COMITI; Sol rad., raising r. hand, globe in l.; stg. l., chlamys across l. shoulder, left field R over X, right field F. In ex. RP RIC VII Rome 27
Licinius I A.D. 315- 316 Ӕ nummus 22x24mm 3.1g IMP LIC LICINIVS P F AVG; laureate draped and cuirassed bust right. IOVI CONSERVATORI AVGG N N; Jupiter standing l., chlamys across l. shoulder, leaning on sceptre and holding Victory on globe in r. hand; eagle with wreath to l. on ground; in right field E. in ex. ANT RIC VII Antioch 17
Crispus A.D. 320 20mm 2.6g IVL CRISPVS NOB CAES; Laureate and cuirassed bust left, spear pointing forward, shield with ✶ on left arm. VIRTVS EXERCIT; Standard inscribed VOT/X with captive seated on ground on either side, in left field S, in right field F over HL. in ex. [A]SIS ✶ RIC VII Siscia 123
Valentinian I. AD 364-375. Æ (16.5mm, 1.34 g, 9h). Uncertain mint. Pearl-diademed, draped, and cuirassed bust right / Emperor right, holding labarum and Victory on globe.
A clashed die occurs when the flan bounces out and the dies hit which leaves an outline, usually of the harder obverse die on the softer reverse.
clashed die on reverse Constantine I A.D. 316 Ӕ nummus 18mm 3.0g IMP CONSTANTINVS P F AVG; laureate, draped and cuirassed bust right. SOLI INVICTO COMITI; Sol rad., raising r. hand, globe in l.; stg. l., chlamys across l. shoulder, in left field M; in right F. In ex. SARL RIC VII Arles 89
A uniface error happened when two flans stuck together and later separated, leaving one side blank
The obverse is either Maximianus, Licinius, Maximinus or Constantine. A.D. 310- 311 Ӕ follis 21mm 4.5g GENIO AVGVSTI CMH; Genius standing left, modius on head, naked but for chlamys over left shoulder, right holding patera from which liquid flows, left cornucopiae. In ex. SMNE Nicomedia
332- 333 18mm 2.5gm Obv: uniface Rev. Victory stg. on prow, holding long scepter in r. hand, and resting l. hand on shield. in ex. TRP✶ RIC VII Trier 548 Ex 1989 Nether Compton (Dorset) Hoard.
VRBS ROMA uniface error The reverse would have been a she-wolf left suckling twins (Romulus and Remus); above, two stars. It looks like an Eastern mint...maybe Nicomedia
here are two flans still stuck together Constantine II A.D. 320 19mm 5.8g D N CONSTANTINO IVN NOB C; laureate, draped and cuirassed bust right. VICTORIAE LAET PRINC PERP; two Victories stg., facing one another, together holding wreath inscribed VOT PR on altar. in ex. P two captives L RIC VII Lyons 90
A mule (or hybrid) happened when mint workers mixed dies that should not have been struck together...like an obverse of Constantine paired with a reverse for a Caesar.
Diocletian A.D. 300- 301 28mm 11.4g IMP C DIOCLETIANVS P F AVG; laureate head right. SACRA MON VRB AVGG ET CAESS N N; Moneta standing left with scales & cornucopiae. In ex. Q thunderbolt cf. RIC VI Rome 100a This coin from Rome has a mintmark of Q thunderbolt; but according to RIC, the Rome mint at this time assigned mints on seniority-- P (Prima was most senior) S, T, Q (Quarta was most junior). So Q should have been only for Galerius. In the footnotes, RIC notes a coin of Maximianus with T; when it should be S (for secunda), and calls it a "hybrid ?"
Constantine II A.D. 326 AE nummus 17x18mm 2.8g CONSTANTINVS IVN NOB C; Laureate, draped and cuirassed bust left. PROVIDEN-TIAE AVGG; campgate, two turrets, no doors, ✶ above. In ex. STR • in crescent cf. RIC VII Trier 479
A.D. 324 CONSTAN-TINVS AVG; Laureate head DOMINOR NOSTROR CAESS surrounding wreath enclosing VOT V star in three lines. in ex. SMH delta Heraclea mint
Constantine I A.D. 328- 329 18mm 3.0g CONSTAN-TINVS AVG; pearl diademed head right. PROVIDEN-TIAE CAES•; campgate, two turrets, no doors, star above. In ex. SMNS RIC VII Nicomedia 153/157-8 (for obv./rev.) Hybrid with Constantine I obverse paired with a Caesar reverse
Constantius II A.D. 325-6 18x19mm 3.3g FL IVL CONSTANTIVS NOB C; Laureate draped and cuirassed bust left. PROVIDEN-TIAE AVGG; campgate, two turrets, no doors, star above. In ex. SMNΔ RIC VII Nicomedia -- This Constantius II is paired with a reverse for Constantine I. The reverse is either RIC VII Nicomedia 90 (A.D. 324- 5) or RIC VII Nicomedia 155 (A.D. 328- 9)
Constantine I A.D. 325- 326 Ӕ nummus 20mm 2.7g CONSTAN-TINVS AVG; laureate head right. PROVIDEN-TIAE CAESS; campgate with two turrets and star above. In exergue SMKB • cf. RIC VII Cyzicus 34
Constantine II A.D. 325- 326 Ӕ nummus 18x19mm 3.8gm CONSTANTINVS IVN NOB C; Laureate, draped and cuirassed bust left. PROVIDEN-TIAE AVGG; campgate with two turrets and star between them. in ex. SMKE• cf. RIC VII Cyzicus 37 mule…paired with a Constantine I reverse (RIC VII Cyzicus 34)
Mystery
The reverse of this brockage has a line running under the portrait. Any ideas? It seems it was on the planchet before striking 21mm 2.9g IMP CONSTANTINVS P F AVG

A brockage occurs when the coin gets stuck to the die and the next strike produces a mirror image on one side of the planchet.

These are fairly common; though reverse brockages are rarer than obverse, because the mint worker could more easily see if the planchet was stuck to the obverse die.

This is a reverse brockage for Gallienus (A.D. 260- 268)

The reverse is AETERNITAS AVG, Saturn with harpa standing right; PXV in exergue. RIC 606

obverse brockage

Tetricus I
271-274
17mm 2.3g

Partial reverse brockage

Constantine I
A.D. 320
18x19mm 2.3g
CONST-[ANTINVS AVG]; helmeted and cuirassed bust right.
VIRTVS EXERCIT, [Valor of the army] Standard inscribed VOT/XX with captive seated on ground on either side, S-F across fields.
in ex. AQ[P]
RIC VII Aquileia 48

Constantine I partial reverse brockage VIRTVS
EXERCIT Aquileia

Obverse brockage

Constantine I
A.D. 320
17mm 3.6g
CONS-TANTINVS AVG; high crested helmet (bowl shaped) and cuirassed bust right.
For reverse see-- VICTORIAE LAET PRINC PERP; two Victories stg., facing one another, together holding shield inscribed VOT PR on altar.
in ex. P [2 captives] L
RIC VII Lyons 79

Obverse brockage

Constantine I
19x20 3.0
SOLI INVICTO COMITI
Rome

obverse brockage

Constantine I
20x21mm 3.3g
IOVI CONSERVATORI
Siscia

Obverse brockage

Constantine I
A.D. 318- 320
20x21mm 3.2g
Siscia mint
should have been VICT[ORIAE] LAETAE PRINC PERP reverse

This Constantine I brockage has a line under the reverse bust. For some obscure reason, somebody did this to the flan before striking; which is why the bust obscures most of it.

21mm 2.9g
IMP CONSTANTINVS P F AVG

Constantinopolis brockage from Trier

15mm 1.8g

Ex 1989 Nether Compton (Dorset) Hoard

Constantinopolis brockage Nether Compton Hoard

Helena
AD 324-330
Æ Follis 13mm 1.5g
Obverse brockage

Obverse brockage

Constantius II

16mm 1.7g

A double strike occurs when the hammer "bounces" which allows the coin flan to move in between strikes. These double strikes can vary from barely discernible to coins that have complete 180 degree rotation.

This Aurelian was struck and then flipped 180 and struck again.

Aurelian
A.D. 270- 275
IMP C AVRELIANVS AVG; radiate & cuirassed bust left.
SOLI INVICTO•; Sol stg. left, right hand raised, left holding globe, at foot captive; ✶ in left field .
In ex. KA
RIC Vi Tripolis 390

Maximianus
A.D. 285- 286
Æ Antoninianus 23mm 3.1g
IMP MAXIMIANVS P F AVG; radiate, draped and cuirassed bust right.
IOVI CONSERVAT AVGG; Jupiter standing left, leaning on sceptre and holding thunderbolt.
In ex. XXIT
RIC Vii Rome 506

Constantine I
A.D. 314- 315
21mm 3.7g
IMP CONSTANTINVS P F AVG; laureate, draped and cuirassed bust right.
SOLI INVIC-TO COMITI; Sol rad., raising r. hand, globe in l.; stg. l., chlamys across l. shoulder, left field R over X, right field F.
In ex. RP
RIC VII Rome 27

Licinius I
A.D. 315- 316
Ӕ nummus 22x24mm 3.1g
IMP LIC LICINIVS P F AVG; laureate draped and cuirassed bust right.
IOVI CONSERVATORI AVGG N N; Jupiter standing l., chlamys across l. shoulder, leaning on sceptre and holding Victory on globe in r. hand; eagle with wreath to l. on ground; in right field E.
in ex. ANT
RIC VII Antioch 17

Licinius I
double strike IOVI Antioch 17

Crispus
A.D. 320
20mm 2.6g
IVL CRISPVS NOB CAES; Laureate and cuirassed bust left, spear pointing forward, shield with ✶ on left arm.
VIRTVS EXERCIT; Standard inscribed VOT/X with captive seated on ground on either side, in left field S, in right field F over HL.
in ex. [A]SIS ✶
RIC VII Siscia 123

Valentinian I. AD 364-375. Æ (16.5mm, 1.34 g, 9h). Uncertain mint. Pearl-diademed, draped, and cuirassed bust right / Emperor right, holding labarum and Victory on globe.

A clashed die occurs when the flan bounces out and the dies hit which leaves an outline, usually of the harder obverse die on the softer reverse.

clashed die on reverse

Constantine I
A.D. 316
Ӕ nummus 18mm 3.0g
IMP CONSTANTINVS P F AVG; laureate, draped and cuirassed bust right.
SOLI INVICTO COMITI; Sol rad., raising r. hand, globe in l.; stg. l., chlamys across l. shoulder, in left field M; in right F.
In ex. SARL
RIC VII Arles 89

A uniface error happened when two flans stuck together and later separated, leaving one side blank

The obverse is either Maximianus, Licinius, Maximinus or Constantine.

A.D. 310- 311
Ӕ follis 21mm 4.5g
GENIO AVGVSTI CMH; Genius standing left, modius on head, naked but for chlamys over left shoulder, right holding patera from which liquid flows, left cornucopiae.
In ex. SMNE
Nicomedia

332- 333
18mm 2.5gm
Obv: uniface
Rev. Victory stg. on prow, holding long scepter in r. hand, and resting l. hand on shield.
in ex. TRP✶
RIC VII Trier 548

Ex 1989 Nether Compton (Dorset) Hoard.

Constantinopolis
uniface error Trier Nether Compton Hoard

VRBS ROMA uniface error

The reverse would have been a she-wolf left suckling twins (Romulus and Remus); above, two stars.

It looks like an Eastern mint...maybe Nicomedia

here are two flans still stuck together

Constantine II
A.D. 320
19mm 5.8g
D N CONSTANTINO IVN NOB C; laureate, draped and cuirassed bust right.
VICTORIAE LAET PRINC PERP; two Victories stg., facing one another, together holding wreath inscribed VOT PR on altar.
in ex. P two captives L
RIC VII Lyons 90

A mule (or hybrid) happened when mint workers mixed dies that should not have been struck together...like an obverse of Constantine paired with a reverse for a Caesar.

Diocletian
A.D. 300- 301
28mm 11.4g
IMP C DIOCLETIANVS P F AVG; laureate head right.
SACRA MON VRB AVGG ET CAESS N N; Moneta standing left with scales & cornucopiae.
In ex. Q thunderbolt
cf. RIC VI Rome 100a

This coin from Rome has a mintmark of Q thunderbolt; but according to RIC, the Rome mint at this time assigned mints on seniority-- P (Prima was most senior) S, T, Q (Quarta was most junior). So Q should have been only for Galerius. In the footnotes, RIC notes a coin of Maximianus with T; when it should be S (for secunda), and calls it a "hybrid ?"

Diocletian
SACRA MON VRB AVGG ET CAESS N N Rome 100a mule
hybrid

Constantine II
A.D. 326
AE nummus 17x18mm 2.8g
CONSTANTINVS IVN NOB C; Laureate, draped and cuirassed bust left.
PROVIDEN-TIAE AVGG; campgate, two turrets, no doors, ✶ above.
In ex. STR • in crescent
cf. RIC VII Trier 479

A.D. 324
CONSTAN-TINVS AVG; Laureate head
DOMINOR NOSTROR CAESS surrounding wreath enclosing VOT V star in three lines.
in ex. SMH delta
Heraclea mint

Constantine I
A.D. 328- 329
18mm 3.0g
CONSTAN-TINVS AVG; pearl diademed head right.
PROVIDEN-TIAE CAES•; campgate, two turrets, no doors, star above.
In ex. SMNS
RIC VII Nicomedia 153/157-8 (for obv./rev.)

Hybrid with Constantine I obverse paired with a Caesar reverse

Constantius II
A.D. 325-6
18x19mm 3.3g
FL IVL CONSTANTIVS NOB C; Laureate draped and cuirassed bust left.
PROVIDEN-TIAE AVGG; campgate, two turrets, no doors, star above.
In ex. SMNΔ
RIC VII Nicomedia --

This Constantius II is paired with a reverse for Constantine I. The reverse is either RIC VII Nicomedia 90 (A.D. 324- 5) or RIC VII Nicomedia 155 (A.D. 328- 9)

Constantine I
A.D. 325- 326
Ӕ nummus 20mm 2.7g
CONSTAN-TINVS AVG; laureate head right.
PROVIDEN-TIAE CAESS; campgate with two turrets and star above.
In exergue SMKB •
cf. RIC VII Cyzicus 34

Constantine II
A.D. 325- 326
Ӕ nummus 18x19mm 3.8gm
CONSTANTINVS IVN NOB C; Laureate, draped and cuirassed bust left.
PROVIDEN-TIAE AVGG; campgate with two turrets and star between them.
in ex. SMKE•
cf. RIC VII Cyzicus 37

mule…paired with a Constantine I reverse (RIC VII Cyzicus 34)

Constantine II campgate mule from Cyzicus

Mystery

The reverse of this brockage has a line running under the portrait. Any ideas?

It seems it was on the planchet before striking

21mm 2.9g

IMP CONSTANTINVS P F AVG