Princess Sibylla of Saxe-Coburg and Gotha (Sibylla Calma Marie Alice Bathildis Feodora), the mother of the current King of Sweden, Carl XVI Gustaf. A member of the House of Saxe-Coburg and Gotha, Sibylla became a Swedish princess by marrying Prince Gustaf Adolf, Duke of Västerbotten, who did not live to ascend the Swedish throne.
Princess Sibylla is wearing the classic diamond and oval cabochon sapphire necklace. The high quality sapphires are surrounded by diamonds and set in gold. There are five pendants which can be removed and worn as earrings. The earrings that the Princess is wearing may have been additional pendants on the necklace.
The sapphires for this wonderful necklace were a wedding gift from her uncle, Ferdinand (from the house of Saxe-Coburg-Gotha), the Tsar of Bulgaria to Princess Sibilla of Saxe-Coburg-Gotha, on the occasion of her wedding in 1932 with the then future crown prince of Sweden Gustaf Adolf.
Her daughter princess Brigitte has often been seen in public wearing the same necklace, her being the only person ever seen wearing it since it was seen in Princess Sibylla's neck, which leads me to believe she has inherited it from her mother
Princess Sibylla and indeed her daughter on the picture on the right, are also wearing another gem from the vast jewel stores of the Swedish royal family, the Connaught Tiara.
This exquisite tiara has 5 distinctive upright loops of forget-me-not wreaths with a diamond pendant suspended in each.
Between the loops, upside down bows support single diamond uprights. It was a wedding gift to Princess Margaret of Connaught from her parents, the Duke and Duchess of Connaught, when she married Prince Gustaf Adolf of Sweden (the future King Gustaf VI Adolf) in 1905.
Margaret died in 1920, and her son (also called Gustaf Adolf) gave it to his bride Princess Sibylla of Saxe-Coburg and Gotha as a wedding present in 1932. It was a favorite of hers, and is still often called Princess Sibylla's Tiara.
By the time Queen Silvia married into the Swedish royal family, Princess Sibylla had passed away and her son Carl Gustaf was king. Silvia chose this piece for her first public tiara appearance at her pre-wedding gala (above, far left) and she continues to wear it to this day.
Other royal family members have worn it since Sibylla's passing, though, including Princess Christina on her wedding day and Princess Madeleine on Crown Princess Victoria's wedding day. Crown Princess Victoria herself first wore the full tiara in 2015, to Prince Carl Philip's wedding.