Within the European Wine Industry Association, there is actually a set of "non-standard ratings" for fine wines that is not disclosed to the public.
An "A-grade" wine, if it's a blended wine, reaches a master-level standard.
Whereas "S-grade" signifies supreme, rare existence. Typically, "S-grade" comes from the hands of a Great Master, a masterpiece of the Great Master's craftsmanship.
Of course, there are exceptions, such as the rating of "Encounter" wine, which also belongs to the "S-grade", yet is not the handiwork of a Great Master.
However, among the ingredients used in "Encounter", there is one that is considered rare grade.
In fact, every "S-grade" wine, if not made of rare materials, at least employs extremely high-quality, very rare components.
For example, a particular wine must use a specific grape from a certain region, and even from the best selection, as any slight variance could affect the taste.
