Around 175-125 BC, a silver tetradrachm coin was minted in Mesembria, Thrace in the name of Alexander III of Macedon. The coin is in very fine plus condition and weighs 16.10 grams with a diameter of 31 mm. 

The obverse side features a head of Herakles facing right, adorned with a lion skin headdress. The reverse side depicts Zeus Aetophoros seated to the left, holding a scepter, with the inscription "BAΣIΛEΩΣ" below and "AΛEΞANΔPOY" to the right. Above Zeus is a crested Corinthian helmet, and in the left field are the letters ΔΑ, with the monogram HPA below the throne.

This historical coin is a valuable piece from the ancient Thracian region and is a testament to the rich history of the area during that time period.