Good question...
To me, the statement that each store has a unique understanding and ethic of grading is key.
'Freshadama' were lucky to find the operation capable to bring them to the market, and expert to define and publicize the grade and this forum.
It is lucky too that pearl grades do not depend on some 'black box' operation (hint: diamond grades :roll-eyes: )- a pair of eyes and experience are supposed to be enough. And having seen or owning a few great pearls constitute experience... The tradition of pearl grading is quite reassuring covering the basis - a dozen or so centuries must have been enough to decide what the best pearls biologically possible look like...
Wanna do you own? Owning a few great ones should teach the right lesson. And examples of even very fine pearls are not extraordinarily expensive by gem standards.
In case this sounds crazy, well, I didn't invent the practice: professional buyers of precious stones carry sets of reference stones - a historic practice. Unlike pros, I can't pretend to own the right samples for everything interesting including most of the dozens of types of natural pearls (!), but to some extent visual memory works too for my unambitious use. It looks like Zeide's closet is among the best 'pearl-grading labs' for this reason.
Posting on other forums, I used to have as tag a quote from Souren Melikian, the art critic:
"Experts are as good as the sum total of what they have seen" - couldn't find a better mantra of gem grading since!
My 2c...
