Hello !
Interesting topic.
I think that at a certain era, what was called sautoirs was very long necklaces, most of the time made of one or several ropes of pearls.
When I think about long sautoir of the beginning of the 20th century, I have Queen Margherita of Italy (very famous for her pearl sautoirs) and Empress Zita of Austria who had a very long pearl sautoir.
In most recent time, I think we can talk more about 'long necklaces' than sautoirs beeing worn.
Hereditary Princess Stephanie pearl long necklace is a good exemple.
I think we can add to this, the long (diamond ?) chain necklace worn by Crown Princess Marie Chantal of Greece in Denmark, during Crown Prince Frederik’s 50th Birthday Gala in May 2018 and Queen Maxima, wearing a long necklace of gold, opals and diamonds during visits in Australia and India.
Thanks and have a good week-end !
J-F