Metallic actually refers to luster typically with an undertone of color.
What differentiates freshadama is that we use loose grade pearls to make the line. In other words, we use pearls that are typically sold individually or by weight for use in earrings, pendants and other single-pearl pieces. We buy the pearls loose and have them drilled for strands. As far as I know, we're the only company in the world that does this with freshwater pearls on a large scale.
Without a standardized system, one company's AA+ could (and does) exceed standards for another's AAAA. There is typically one grade higher than "highest necklace grade" available at the shows from most of the large processors. This grade is often marketed as higher than AAA, but don't mistake it for AAAA. There are only a couple of companies using this designation and they sell at a price less than the wholesale cost of the higher grades - because there is no recognized, standardized system.
One easy way to gauge is in the sizing. Fine freshwater pearls under 9 mm are always measured in half millimeter sizes. In other words, they are 6-6.5 mm, 7-7.5 mm or 7.5-8 mm. They are never created in full millimeter increments, such as 6-7 mm, except in the larger sizes.
When sold in full millimeter increments, such as 7-8 mm, the smallest pearls will actually be as small as 6.5 mm at the ends, and the largest around 7.5 mm. Within the strand, approximately 75% of the pearls are in the smallest half and 25% in the larger. It's because the raw pearls are sold by weight. They're sometimes referred to as commercial grade.