12.5-13.5mm. AA Grade Natural Coin Pearls. The luster and quality of these coin pearl beads will amaze for sure! You receive one strand of pearls. The luster is as beautiful as the photo. The shape is very consistent which is a rare find with coin pearl beads. Freshwater coin pearl beads are created when a small flat disc shaped shell, instead of a round bead, is inserted into the oyster or more commonly these days, mussel. Most of these pearls are farmed in rivers, lakes or streams. The result is a a fabulous flat disc shape pearl. Our freshwater coin pearl beads are picked by their luster and size.