Dawn and I have had email exchanges about that. Those earrings, and the other jewelry in that style, were made in the 20's through the 40's in Oaxaca. There had been some kind of pearl farm going on at some point that harvested farmed, natural pearls, but it is unknown whether it ever supplied pearls for the Oaxacan jewelry. However, the crowd that wore those revival Oaxacan earrings from that era were the upper classes and intelligentsia that wore ethnic jewelry -after Frida's circles embraced the ethnic look as did their American and European associates. The jewelers were perfectly aware of how to get those low grade pinctada radiata pearls from the Persian Gulf, even though neither Dawn nor I have seen any sales receipts or anything like that kind of proof.
Is is known that the Spaniards brought Moorish filagree work to the New World and the master gold and siver smiths of Mexico learned it as they chose. Therefore it is not really indigenous, and was always primarily worn by Mestizos and Spaniards. Oaxacan metal smiths in particular specialized in the filagree and the jewelry and other products were often gifted on special occasions, like coming of age and marriage. Marriage was especially associated with wearing all one's white pearls and this was an entirely Euro association. Senoritas could wear white pearls; the earrings given before marriage continued to be worn after marriage, too. I think there was at least one family from India, who sold pearls in Mexico City for the upper class, and maybe, one in Monterrey, too. Those small irregular pearls have always been at the bottom end and by far the most plentiful of all Persian Gulf pearls. Oaxacan style jewelry was/is a brilliant use of them.
