Vintage obsidian and sterling brooch made in Mexico

Gorgeous statement brooch. Changes colour from black to a golden shimmer. Initialed and stamped sterling. Has some surface mark wear mostly near the top and the back is tarnished. Would shine up beautifully but will leave that up to the new owner since some like their silver darker then others or prefer a certain way to polish. Bright white lines are from overhead lighting. Enclosure works well but opens mid way rather then the full rotation. I used this on a small black clutch for years and recently the purse gave out and I dont wear much jewelry, I just collect pieces and use them in other ways. This would be a nice accent on a gown or used as a necklace or on a hat or bag not just as a brooch. Please see photos for the best description thank you