Vintage Senator Single Black Bull Cufflink

This (single) vintage cufflink by Senator is made of a gold tone metal and has a rounded toggle. The cufflink is shaped like a soft square with the center cutout. There is center square piece held in place by the outer frame, and it features a left-facing bull in a black material. Because of how it's set, it's hard to test the material, so I can't confirm anything. My best guess would be onyx, but again, it's a maybe. The cufflink has normal vintage wear but is still wearable, it just doesn't have a mate. Dimensions: 21x19mm Weight: 7.15g Love the piece but not the price? Make an offer!