The Hemidrachm denomination — Variants: Triobol
The Hemidrachm was an ancient Greek coin denomination with a value of 3 obols, which is half a drachm. it is also often called a triobol.

The hemidrachm generally weighs around 2.15 grams when struck in silver, but was also struck in bronze.
Hemidrachm|Triobol
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An AR Hemidrachm struck c. 86 BC in Dyme
Obverse: head of laureate Zeus right

Reverse: fish under (AX) monogram all within wreath; (APT) left / ΔY up

Diameter: 15.5 mm
Die Orientation: -
Weight: 2.2 g
ex Forum Ancient Coins
Clerk 55; BCD Peloponnesos 482
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An AR Hemidrachm struck 160-146 BC in Megalopolis
Obverse: laureate head of Zeus right

Reverse: (AX) monogram, thunderbolt below, all within wreath; ΞB / K_A / M

Diameter: 15.5 mm
Die Orientation: -
Weight: 2.4 g
No notes for this coin
Benner 17; BCD Peloponnesos 1551.1; HGC 5, 953
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An AR Hemidrachm struck c. 188-180 BC in Mantineia
Obverse: laureate head of Zeus right

Reverse: (AX) monogram within wreath; A_N / CΩ

Diameter: 17 mm
Die Orientation: -
Weight: 2.4 g
Mantinea as Antigoneia
Benner 5; BCD Peloponnesos 1492.2; HGC 5, 926
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An AR Hemidrachm struck c. 175-168 BC in Megara
Obverse: laureate head of Zeus Amarios right

Reverse: lyre above (AX) monogram, all within wreath; ΔΩ_PO

Diameter: 14.5 mm
Die Orientation: -
Weight: 2.3 g
No notes for this coin
BCD Peloponessos 27.1; McClean 6431-2, Benner S. 78, 4; HGC 4, 1805
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An AR Hemidrachm struck 100-80 BC in Pallantion
Obverse: laureate head of Zeus right

Reverse: (AX) monogram, trident below, all within wreath; A / Π_Λ / (YE)

Diameter: 14 mm
Die Orientation: -
Weight: 2 g
No notes for this coin
BCD Peloponnesos 1593.2; Benner 4; HGC 5, 969
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An AR Hemidrachm struck c. 350-300 BC in Apollonia Pontica
Obverse: facing head of Medusa

Reverse: anchor flukes up; A / crayfish

Diameter: 12.5 mm
Die Orientation: -
Weight: 3.24 g
No notes for this coin
Apollonia p. 347, 1; SNG BM Black Sea 160-1, SNG Cop. 456ff
(7) Argos
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An AR Triobol struck 125-80 BC in Argos
Obverse: forepart of dog

Reverse: big A, trident below; Δ _ A / MAP

Diameter: 15 mm
Die Orientation: -
Weight: 2.03 g
No notes for this coin
BCD Peloponnesos 1145; SNG Copenhagen 47-8
(8) Byzantion
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An AR Hemidrachm struck 387-340 BC in Byzantion
Obverse: forepart of cow left, below dolphin swimming left; (BY)

Reverse: wide ornamented trident

Diameter: 10 mm
Die Orientation: -
Weight: 1.9 g
No notes for this coin
Schönert-Geiss Byzantion 778; SNG BM 17; Klein 88; SNG Cop 484 var. (monogram); BMC Thrace p. 94, 23 var. (same), SGCV I 158
(9) Cherronesos
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An AR Hemidrachm | Triobol struck 386 - 338 BC in Cherronesos (Thrace)
Obverse: Forepart of lion right, head reverted

Reverse: Quadripartite incuse square with alternating raised and sunken quarters; pellet in one sunken quarter, wreath in the opposite

Diameter: 13 mm
Die Orientation: -
Weight: 2.09 g
No notes for this coin
McClean 4076-7; HGC 3, 1437
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An AR Hemidrachm struck 400-350 BC in Cherronesos (Thrace)
Obverse: forepart of lion right, head turned back

Reverse: quatripartite incuse square, grain ear in one section, X· in other

Diameter: 12 mm
Die Orientation: -
Weight: 2.25 g
No notes for this coin
McClean 4103 var (dot over E)
(11) Kroton
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An AR Triobol struck c. 430-420 BC in Kroton
Obverse: Pegasos left; Ϙ

Reverse: Tripod with 3 ring handles and legs ending in lion’s paws; ϘPO

Diameter: 11 mm
Die Orientation: -
Weight: 1.5 g
Kroton had the rather curious practice of issuing fractions bearing reverse types taken from the coinage of other cities: such as, among others, the Pegasus of Corinth (complete with the letter koppa below), the hare of Messana and the octopus of Syracuse.
HN Italy 2127, SNG Cop 1788
(12) Lokri Opuntii
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An AR Triobol struck c. 340-330 BC in Lokri Opunti
Obverse: Head of Persephone right wearing wreath of grain, single-pendant earring, and pearl necklace

Reverse: Ajax the Lesser (son of Oileus) nude but for crested Corinthian helmet advancing right in fighting attitude holding short sword and shield on left arm ornamented inside with coiled snake (control symbol), helmet crest below; OΠONTIΩN

Diameter: 15 mm
Die Orientation: -
Weight: 2.7 g
No notes for this coin
SNG Cop.51, de Nanteuil 886, BCD Lokris-Phokis 96
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An AR Hemidrachm struck c. 424-350 BC in Neapolis (Macedonia)
Obverse: facing head of Medusa (Gorgoneion), tongue protruding

Reverse: diademed female head right; NEOΠ

Diameter: 13 mm
Die Orientation: -
Weight: 2 g
No notes for this coin
SNG ANS 430-454; SNG Cop 227; SNG Berry 41; BMC Macedonia p.85, 17; SGCV I 1417
(14) Odrysian Kingdom | Parion imitative
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An AR Hemidrachm struck 500-350 BC in Thrace
Obverse: head of Medusa (Gorgoneion) facing

Reverse: incuse square with cross and pellet

Diameter: 13 mm
Die Orientation: -
Weight: 1.71 g
Forum note: "This type has traditionally been attributed to Parion, Mysia or as a Celtic imitative of the Parion type. Based on find locations in the area of Plovdiv, Haskova, Stara Zagora and Yambol in Bulgaria, Topalov has reattributed this imitative type to the Thracian Odrysian Kingdom. He notes they may have been struck by a tribal mint or by one of the Greek cities within Odrysian territory to pay their annual tax to the tribe."
cf.SNG France 1347; cf.SNG Copenhagen 256
(15) Olympia
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An AR Hemidrachm struck 312-271 BC in Olympia
Obverse: laureate head of Zeus right

Reverse: eagle right; olive leaf right; F _ A

Diameter: 14 mm
Die Orientation: -
Weight: 2.65 g
No notes for this coin
BMC 84. Dewing 1896. McClean 6637. SNG Delepierre 2158
(16) Parion
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An AR Hemidrachm struck c. 350-300 BC in Parion
Obverse: head of Medusa facing (Gorgoneion)

Reverse: bull standing left, head turned right; dolphin above; Π_A / PI

Diameter: 12 mm
Die Orientation: -
Weight: 2.5 g
No notes for this coin
BMC 22
(17) Pharkadon
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An AR Hemidrachm struck c. 420-400 BC in Pharkadon
Obverse: Thessalos, wearing petasos and chalmys, right restraining bull with cord around bull's forehead held in both hands

Reverse: forepart of galloping horse right; Φ_A_P_K / AΔ_O

Diameter: 15 mm
Die Orientation: -
Weight: 2.8 g
No notes for this coin
BCD Thessaly II 603; BMC Thessaly p. 42, 1; SNG Cop 209; HGC 4 292
(18) Pharsalos
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An AR Hemidrachm struck c. 450-400 BC in Pharsalos
Obverse: helmeted head of Athena right

Reverse: head of horse right; Φ A / P Σ

Diameter: 15 mm
Die Orientation: -
Weight: 2.87 g
No notes for this coin
Lavva 75 (V38/R44)
(19) Phasis?
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An AR Hemidrachm struck c. 425-325 BC in Phasis?
Obverse: Archaic female head (Artemis Dali) right

Reverse: Head of bull right

Diameter: 11 mm
Die Orientation: -
Weight: 2.1 g
No notes for this coin
SNG BM 1013-1018; Hind 7; HGC 7, 215
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An AR Triobol struck c. 440-420 BC in Daulis?
Obverse: facing bull head

Reverse: head of Artemis right; Φ O K I

Diameter: 13 mm
Die Orientation: -
Weight: 2.9 g
No notes for this coin
SNG Cop 99 ff.
(21) Rhodos
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An AR Triobol struck 170-150 BC in Rhodos
Obverse: Radiate head of Helios facing slightly right

Reverse: APTEMΩN / P-O, rose with bud to right, hook to left; all within incuse square.

Diameter: 13.1 mm
Die Orientation: 11 H
Weight: 1.16 g
"Plinthophoricï" coinage. Artemon, magistrate. 
Jenkins 50; SNG Helsinki 658. VF
(22) Sikyon
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An AR Hemidrachm struck c. 330-280 BC in Sikyon
Obverse: Chimera walking left; ΣI

Reverse: dove flying left, •

Diameter: 15 mm
Die Orientation: -
Weight: 2.79 g
No notes for this coin
BCD Peloponnesos 292; SNG Cop 64; BMC Peloponnesus p. 46, 124
(23) Sikyon
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An AR Triobol struck an unknown year in Sikyon
Obverse: Dove flying left

Reverse: M Monogram

Diameter: 11 mm
Die Orientation: -
Weight: 2.1 g
SIKYONIA, Sikyon
SNG Copenhagen 103
(24) Tanagra
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An AR Hemidrachm struck 457-448 BC in Tanagra
Obverse: Boeotian shield

Reverse: forepart of horse right within incuse square; T_A

Diameter: 11 mm
Die Orientation: -
Weight: 3.1 g
No notes for this coin
Dewing 1498 (same rev. die)
(25) Teos
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An AR Hemidrachm struck c. 500-460 BC in Teos
Obverse: Griffin seated right

Reverse: rough incuse square

Diameter: 12 mm
Die Orientation: -
Weight: 2.6 g
No notes for this coin
Balcer group XXI, 51-6; SNG Copenhagen 1434
(26) Thebes
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An AR Hemidrachm struck 426-395 BC in Thebes
Obverse: Boeotian shield

Reverse: Kantharos; club above; Θ_EB

Diameter: 12 mm
Die Orientation: -
Weight: 2.52 g
No notes for this coin
BMC 64; SNG Cop. 289
(27) Trikka
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An AR Hemidrachm struck c. 480-400 BC in Trikka
Obverse: naked Thessalian youth standing right, restraining forepart of unruly bull prancing right

Reverse: forepart of bridled horse prancing right, within incuse square TPI_KK_AI (retrograde)

Diameter: 16 mm
Die Orientation: -
Weight: 2.56 g
No notes for this coin
SNG Oxford 3933; BCD Thessaly II 768; BCD Thessaly I 1351