Vintage Pearl Pastel Ivory-White Glow, 1/2" Real Shell 13mm, Self-Shank Pack of 12 #VB-27

These match the 'wondrous tiny one, VB-24, but these are 9/16" diameter, much larger, also with a wondrous glow and lustre. The tops are flat with rounded edges, sleek and shiny with lots of iridescence and blending of whites and ivories. Self shank with an opening around 1.75mm. Real shell, probably Trocas, from 'back in the day',  perhaps 1930's-50's. They look and feel much like glass. They seem undyed; maybe the natural shell's color, polished?  Sold per pack of 12.