19th Century 18ct Gold & Onyx Ring With Coronet & Two Keys

A very unusual 18ct75% pure gold (or 750 parts pure gold and 250 parts other metals) gold ring that was made circa 1880. It has been set with a shield shaped onyxOnyx is an opaque black variety of polycrystalline chalcedony quartz.  with an 18ct gold coronet with two keys in a shield shape below. The shouldersThe point on a ring where the central section meets the shank or band, often carved, decorated or inlaid with small diamond accent stones. are a pierced design. Having done some research the Coat of Arms with it’s coronet and keys is for the city of Leiden. The origins are from the 13th century, when the interlocking keys first appeared. The meaning is holding the “keys to heaven” Saint Peter frequently appeared across Leiden imagery during that time. As a result, Leiden is known in the Netherlands as the “Key City”