How did Buckley achieve this? By studying the colophons in manuscript editions of the Ginza, Canonical Prayerbook, Book of John, and other sources including Lady Drower's personal papers and letters given to Buckley by Drower's daughter. Colophons are lists of scribes and the scribal postscripts that are appended to most Mandaean manuscripts. The list of scribes extends from the current copyist all the way back to the first scribe recorded to have copied the manuscript. They present the name of the scribe and his lineage. It is quite genius I think to work through these lists as a way to resurrect Mandaean history.
I find it extremely interesting that some of the names recovered are names of women priests who were initiated into the religion by their biological fathers who were priests. This view is against the dominant one in scholarship, that there weren't ever women Mandaean priests. Buckley says this is wrong, and quotes several present-day Mandaeans who remember their ancestors talking about women priests in the past. Buckley has detected 24 women priests in the Mandaean colophons. The dates for the women she detected: ca. 200, 700, 750-800, 1300, 15th c. to early 16th c., 17th c. to mid-19th c. (pp. 181-182).
In the end, Buckley postulates that the Mandaeans are at least as old as 30 CE, that they left Palestine via the Wadi Hauran route and went to Media. Although they may have initially been a Jewish group connected to John the Baptist, they turned against Judaism in much the same way that the Jewish-Christians polemicized against Paul and pro-Gentile Christianity. She thinks that their Gnostic religiosity is very old, that they may be our oldest example of mid-first-century Gnostics. By 200 CE they were well-established in Media and lived along the trade routes tied to the Silk Road. It is in Media, she suggests, that their traditions absorbed Zoroastrian and maybe Christian ideas. She suggests that "we view the Mandaeans as the earliest example of a wide-ranging group - possible moving from Palestine to Media - creating our first evidence for Gnostic religiosity" (p. 341).