Victorian-style costume brooch with blue stone

This is a vintage or antique costume jewelry piece, specifically an ornate brooch featuring a large, rectangular emerald-cut light blue paste stone or glass crystal at its center. The mounting is constructed from a dark base metal, possibly brass or a copper alloy, which exhibits a heavily oxidized, aged patina with darker brownish and greenish tones consistent with age and environmental exposure. The metal frame is intricately detailed with repoussé or cast floral and foliate motifs flanking the central stone, bordered by a twisted rope pattern edging. Extending from the back is a thin metal pin stem, suggesting a traditional C-clasp or early safety clasp mechanism, though the reverse side is not fully visible. There are no visible maker's marks, stamps, or signatures discernable on the front of the piece. The overall craftsmanship and design elements are consistent with Victorian or Edwardian revival costume jewelry popular during the late 19th to mid-20th century. The item shows noticeable signs of wear, surface scratching on the central stone, and considerable oxidation on the metal setting, which remains unauthenticated and presents as an unmarked decorative piece.

Based on what I can see in the provided image, this ornate brooch appears to be a vintage or antique piece of costume jewelry, likely reflecting Victorian or Edwardian revival styles popular during the late 19th to mid-20th century. The mounting features a heavily oxidized dark base metal with repoussé floral motifs and a twisted rope border, framing a large, emerald-cut light blue paste or glass stone. I can't verify the exact metal composition, stone material, or age from a photograph alone, and physical inspection would be needed to confirm these characteristics. There are no visible maker's marks or stamps discernable on the front, and the piece shows notable surface scratching on the central stone and considerable oxidation. Assuming this is an antique piece consistent with Victorian-style costume jewelry of the period, comparable items typically trade in the $75 to $150 range on the secondary vintage market, driven by steady demand for wearable antique costume accessories. However, this estimated value is entirely dependent on authentication. If the item were to turn out to be a modern reproduction, replica, or made 'in the style of' rather than a period piece, the value would decrease significantly, likely dropping to the $20 to $40 range. To confirm the piece's age, materials, and overall status, an in-person examination by a qualified jewelry expert, along with potential metal and material testing, would be required.