Antique Victorian Onyx Mourning Brooch Pin

This unique and rare piece appears to be made out of a cylindrical bar of solid Onyx, capped with silver (likely sterling) on each end, with a decorative graduated swirl around the center. The swirl is not firmly attached and can rotate around the piece. There is a long pin on one end of the caps. This is a large and heavy pin, measuring 3" long and just over 1/2" in diameter. Could be worn by men or women, this piece may have been specifically crafted using an object beloved by the decedent. It is in very good shape for it's age, which is most likely from the 1870s-1890s. Not marked.