At no time have I considered the possibility that these amulets are from ancient times. I have assumed they were probably under 100 years old. I have considered whether these particular ornaments, that I have assumed are Persian, were contemporaneous with the so-called "donkey beads" than have been commonplace over my entire career with beads, from the 1960s. But, perhaps surprisingly, in those early years I did not come across the disks. So I've been inclined to suspect they were probably somewhat older than the oblate beads that are much more common.

By the way, I have also seen non-faience imitations of these disk products, a very few times. I think I have one, somewhere.

Giorgio's short exposition is essentially a very quick rendering of the entire history of early faience, and doesn't address your actual question. However, I cannot disagree with what he says.

Jamey