I would say real pearls, but cultivated. But it is just speculation, not a proven certainty.
By the way, Queen Anne-Marie has a very large jewel collection: besides her Greek and Danish historical jewels, she owns a lot of smaller but very fine jewels - including jewels which were seen only after the exile of the Royal Family in 1967 (therefore in a period when the Royal Family was supposed to be less affluent than when they were on the throne...).
--Previous Message-- : Queen Anne Marie is wearing a stunning pearl : necklace. One rarely sees pearls of that : size anymore. Do you think the pearls are : real or costume jewelry? :