The brides wore as tiara the part of the necklace. If you have a good look a the photos of the auction, you can see that the bracelet has a motiv of 2 diamond rows and the necklace 3 rows.
During the wedding of HRH Princess Joséphine-Charlotte, she wore as necklace the Congo-bracelet and as tiara the Congo-necklace and later the Diademe of the Sociéte Générale.