This is a large (7cm diameter) devotional plague with an inscription. Though the parts are worn, the layout suggests: Allah, possible Muhammad / Allah phrases, possibly Ya Ali or other devotional invocation. Talismanic words arranged in protective grid format. Such pieces were believed to bring protection, divine blessing or spiritual authority.
These talismanic plagues were particularly common: in Qajar Persia (late 1700s - 1800s), North India - Pakistan islamic devotional markets (18th - 19th c).
This piece has a lovely green patina.