Cius, later renamed Prusias on the Sea after king Prusias I of Bithynia, was an ancient Greek city bordering the Propontis, in Bithynia and in Mysia, and had a long history, being mentioned by Herodotus, Xenophon, Aristotle, Strabo and Apollonius Rhodius.
Coin of Cius
Prusias I Cholus was a king of Bithynia, who reigned from c. 228 to 182 BC.
Tetradrachm of Prusias I (young)
Tetradrachm of Prusias I (older and bearded). British Museum.