The Siglos denomination
The Siglos was a coin denomination in the Persian Achaemenid Empire, and was roughly equivalent to 7½ Attic obols. It was struck in silver.

In more understandable terms, it generally weighed 5.4 grammes, and was struck from circa 520 BC to 330 BC.

(1) Achaemenid Empire 455-420? BC
Obverse: hero or king holding bow and dagger right
Reverse: incuse square; crescent countermark
Ref: Carradice type IV (early) A
(2) Achaemenid Empire 510/505-486 BC
Obverse: Great King right bearded and crowned kneeling-running, drawing bow, quiver at shoulder
Reverse: incuse square
Ref: Carradice type II: Carradice plate ...
(3) Croesus 561-546 BC
Obverse: Confronted foreparts of a lion and a bull
Reverse: Two incuse square punches
Ref: SNG von Aulock 2877