Dried out akoyas will have slight cracks, and as you handle them, the nacre will flake off.Just thinking about this and wondering...... How would I tell if 70 years in a bank vault box had ruined these??? Would there be cracks or what???
80s and 90s were the worst years for Akoyas, some of them spending as little as 6 months in the water after nucleation. Some of those would actually flake off in the drying lights of a display cabinet
I do have a 3.5 momme strand that has worn down to river mussel bead, but that took a lot of 60s hairspray and abuse.