Online Shop › Tiffany & Co. Antique 18K Yellow Gold Pearl Necklace (Preowned) - 7ty1165 Image 1 of 1 Tiffany & Co. Antique 18K Yellow Gold Pearl Necklace (Preowned) - 7ty1165 $5,650.00 Preowned.Tiffany & Co. Antique 18K Yellow Gold Pearl Necklace. Pearls measure approximately 8.5–9 mm. Add To Cart Added! Preowned.Tiffany & Co. Antique 18K Yellow Gold Pearl Necklace. Pearls measure approximately 8.5–9 mm.