Hi Susan,
I assume they consider these the fine gem grade beyond the A rating system. According to
www.mikimotoamerica.com, "Mikimoto pearls are known as hanadama" which appears to mean that all their pearls are varying degrees of hanadama which is clearly false. The Ginza store also offers "gem grade" which are the absolutely most frivolously priced range comprising cultured akoyas with sufficient nacre to exhibit orient. These are not flawless cultured pearls and none of them are white rosé. Some of them are even noticably bumpy from a distance.
Zeide