Anna, I am curious about the length of the two strands. Looking at the images arranged in historical sequence, the lengths seem to vary a lot.
Princess Augusta
View attachment Outlook (7)
Queen Josephine - 5 pearls between each drop (which seems consistent in other paintings of the necklace). Since this is a painting, I just looked at the number of pearls, not their individual shapes.
Ebba Bernadotte - clearly restrung: short choker length but with 6 pearls between each drop. Note the curious button shaped pear near the center drop. All the pearls seem slightly distorted in this image but there is one that is visibly narrower than the others.
View attachment Outlook (6)
Countess Gertie Bernadotte - Back to a princess length with both strands of a similar length, with six pearls between the drops. The curious shaped pearl seems to be in the same place, two to the left of the center drop
Christie's Catalog (1995) -here, we see the outer strand as much longer than the inner strand, still at choker length. The spacing of the drops is still 6 pearls (so extra pearls would have been added at the back, perhaps? Where did those hypothetical pearls come from?) and the funny shaped pearl from the previous photos isn't anywhere to be found.
Model (2014) - by now, it is clear that this configuration is neither the early to mid 20th century nor the historical configuration. In my opinion, a much less graceful arrangement. No funny pearl here either.
Do you know why this layout was chosen? Is the total length of the necklace consistent or were pearls added or removed over the years? Of course the necklace would have been restrung over the centuries but how do these changes affect price and provenance?