Mesembria, originally a Thracian settlement known as Menebria, became a Greek colony when settled by Dorians from Megara at the beginning of the 6th century BC, and was an important trading centre from then on and a rival of Apollonia (Sozopol).
Remains from the Hellenistic period include the acropolis, a temple of Apollo, and an agora. A wall which formed part of the fortifications can still be seen on the north side of the peninsula.
Bronze and silver coins were minted in the city from the 5th century BC and gold coins from the 3rd century BC. The town fell under Roman rule in 71 BC, yet continued to enjoy privileges such as the right to mint its own coinage.
It is now the city of Nesebar in Bulgaria. If you’re European you might know it better as the city just south of Sunny Beach.
I don’t actually remember when I bought this coins, but I’ve always really liked the design. The Crested Helmet is, of course, one of the most recognizable ancient Greek symbols, and I also like the symmetrical and aesthetically pleasing reverse with MEΣΑ inside the spokes of a wheel.