I get that PS refers to this website.....but what "defines" it? There are references to mentioning it to the preferred vendors such as IDJ, WhiteFlash, etc...
To my knowledge, there are no "set in stone" parameters for "PS quality" stones. I think it generally is a heads up to the vendor that the client is more educated (and more picky!!!) than the average client and probably has high expectations. Just my .02
FWIW, my understanding of the term "PS quality" diamonds is that it refers to the diamond melee in a setting ... of course anything WF or BGD makes in-house is with their respective super-ideal melee diamonds (which are over and above "PS quality"), but other vendors (particularly IDJ among others), have an understanding that many of their Pricescope member customers closely scrutinize their diamond melee and prefer bright and clear melee of a high standard which are closely matched in color, clarity, table, depth.
I placed an order for studs ..IDJ. I forgot to mention PS....in my excitement of purchasing..lol! I will see my studs on Friday. I am NOT really concerned based upon all that i have read about them etc.
FM