Pearl grading is not standard in the jewelry industry. You will typically see grades from AAA to A, and even some such as AAAA or AAAA+. The last two are typically more of a marketing tool than actual difference to other jewelers who use the A to AAA rating.
If it seems confusing, it is. At Wyger & Co Jewelry, we use the A to AAA rating as explained below.
AAA- These pearls are the finest we carry. They will have an almost mirror-like luster to their appearance and a very clean appearance. These pearls will also be almost perfect round in shape.
AA- These pearls are rated for visible natural inclusions and just a bit less of a luster than most AAA. They are also typically round, though some in this category might be more natural in shape, not quite round. This includes baroque pearls, or those with an almost pear-shape to them.
A- These pearls have a nice luster but not as shiny as AAA or AA. They can be near round or misshaped, but still have a nice quality and affordability to them.