A Tetrobol is an ancient Greek denomination worth 4 obols - 2/3rds of a drachm.
It was struck in both bronze and silver.
It was struck in both bronze and silver.

(1)
Histiaia
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Obverse: Head of nymph Histiaia right with wine-wreath
Reverse: Nymph Histiaia seated right on stern of galley, holding stylis; ornate apluster; IΣTI_AIEΩN, trident below
Diameter:
13.5 mm
Die Orientation: -
Weight: 2.3 g
Die Orientation: -
Weight: 2.3 g
No notes for this coin
BMC Central p. 129, 52; SGCV I 2498 var.
(2)
Macedonia

An
AR
Tetrobol
struck c. 187-168 BC
in
Pella
|
Amphipolis
Obverse: head of Maenad right wreathed with vine leaves and grapes, wearing necklace and earrings
Reverse: stern of galley right, star above; MAKE / ΔONΩN, M?
Diameter:
15 mm
Die Orientation: -
Weight: 2 g
Die Orientation: -
Weight: 2 g
No notes for this coin
SGCV I 1384, SNG Cop 1292
(3)
Phaselis
Obverse: Prow of galley right; uncertain controlmark below
Reverse: Stern of galley left; ΦAΣ
Diameter:
14 mm
Die Orientation: -
Weight: 3.4 g
Die Orientation: -
Weight: 3.4 g
No notes for this coin
SNG von Aulock-; Cf Heipp-Tamer 72

An
AR
Tetrobol
struck 323-315 BC
in
Amphipolis
Obverse: head of Apollo wearing tainia right
Reverse: horseman riding right; ΦIΛIΠΠOY, M in wreath
Diameter:
13.5 mm
Die Orientation: -
Weight: 2.52 g
Die Orientation: -
Weight: 2.52 g
Struck by Philip III in the name of Philip II
Le Rider pl. 45, 33; SNG ANS 625-7; SNG Alpha Bank 300