A coin purse was a type of purse for carrying coins.
In 2370, after a Pythron couple decided not to testify against Martus Mazur, Quark quoted the forty-seventh Rule of Acquisition, "don't trust a man wearing a better suit than your own," and claimed Mazur was either a con artist or he was covering up an empty coin purse. Quark knew it to be both. (DS9: "Rivals")