Thessalonica in Macedonia, 1-4 AD., Augustus and Gaius Caesar, Æ21, RPC 1564.

Thessalonica in Macedonia, Augustus and Gaius Caesar,
Æ21 (21-23 mm / 9.36 g), 1-4 AD.,
Obv.: ΘΕΣΣΑΛΟΝΙΚEΩΝ , laureate head of Augustus r.
Rev.: ΓAIOΣ ΣEBAΣTOY YIOΣ , bare head of Gaius r.
RPC 1564 ; BMC 73 .

"Gaios Sebastou Yios": Yios stands for (Greek, transliterated:) huios, son, like filius: "Gaius, the son of Augustus".