A sparkling American post-war / mid-century convertible pendant-brooch from circa 1950, crafted in solid platinum with a high-polished finish and bold retro-modernist patterning. Designed for versatility, it features a hinged pin bar for brooch wear and a concealed ring to suspend from a chain or necklace. The jewel is centered by a gem-quality Australian black opal—a round cabochon measuring 8 x 8 x 4 mm and weighing approximately 1.60 carats—showing a vivid, multi-color play-of-color, and is surrounded by an exceptional diamond arrangement totaling 84 diamonds: 6 prong-set round brilliant cuts totaling 0.48 ctw, 70 flush-set European round and round brilliant cuts totaling 2.84 ctw, and 8 channel-set straight baguette cuts totaling 0.72 ctw (all approximately F color, VS2 clarity). The piece weighs 14.30 g (9.17 dwt) and measures 53 x 36 mm (2.08 x 1.42 in). Unmarked and electronically tested as platinum; accompanied by a presentation jewelry box and in excellent condition, showing only light normal wear, with no damage to the platinum and all stones secure, and the piece carefully inspected to confirm condition and authenticity. Very good conditions. All our diamonds and colored gemstones are naturally earth-mined. Any synthetic (lab-grown) stones will be clearly indicated in the description. Upon Request, Auction House may provide an appraisal. This will carry an additional cost. Appraisals are made by our in house GIA certified Gemologist.