'Thought the next two make a rather interesting example of something. Just not sure of what !?
What could have made such a difference for how these two pear rings endured?
Not sure if the links to individual items work. They are lot No.616 and No.638 in the latest Fine Jewelry auction (
Sale 2375) at Skinner.
Click on the thumbnails below for full blown pictures:
Sale 2375 Lot 616: Edwardian Pearl and Diamond Ring, set with a pearl flanked by old mine and old single-cut diamonds, platinum-topped gold mount, size 2 1/2. Estimate $500-700. (Sold for: $3642) 
Sale 2375 Lot 638: Art Deco Platinum, Pearl, and Diamond Ring, bezel-set with an ivory tone pearl with rose overtones, measuring approx. 3.55 mm, shoulders set with baguette-cut diamonds, size 3 3/4, (pearl with damage). Estimate $700-900. (Sold for: $760)
I would guess that the estimates were meant to reflect the value of the vintage settings, mostly... Which turned out right for the one with the damaged pearl. And the hammer price of the undamaged pearl may reflect the buyer's direct examination of the pearl in person (that might have amended the dull picture) and high hopes that the pearl might be natural.
Sorry for the adds on Imageshack
Not much I can do about that... and still post large pictures.