Commenting on the silver amulets discovered at Ketef Hinnom, Ronald Hendel and Jan Joosten wrote:
The archaeological and paleographical evidence agree in dating these inscriptions to the late seventh or early sixth century BCE. These tiny amulets contain prayers that are closely related to the Priestly and Deueronomic texts.
The first amulet begins:
יהו [. . . ] גד [. . . ] הברית ו[. . . ] חסד לאהב [. . .] ושמרי [. . .]ד העלמ
Yahwe[h . . .] grea[t . . . ] the covenant and [. . . ] steadfast love for those who love [. . . ] and keep [ . . .f]orever
This sequence is close to the language of Deut 7:9:
יְהוָה . . . שֹׁמֵר הַבְּרִית וְהַחֶסֶד לְאֹהֲבָיו וּלְשֹׁמְרֵי מִצְוֹתָיו לְאֶלֶף דּוֹר
Yahweh . . . who keeps the covenant, and steadfast love for those who love him and who keep his commandments, to the thousandth generation.
The Deuteronomy passage is, in turn, related to—and perhaps an allusion to—the Deuteronomic language in the First Commandment (Exod 20:6 = Deut 5:10). Close echoes of the language of Deuteronomy and the Decalogue are here found in a preexilic inscription. This does not mean that the amulet itself is necessarily quoting or alluding to the book of Deuteronomy, but it does show that Deuteronomic formulations were current in the late preexilic period. This amulet echoes the C[lassical]B[iblical]H[ebrew] language of Deuteronomy and is consilient with the preexilic context of the core of Deuteronomy. If one holds that Deuteronomy and the Deuteronomic movement were products of the Persian period or later, then this parallel language is a problem.
This condition also holds for the near-verbatim quotation of the Priestly Benediction in both amulets. We infer that this prayer, found in Num 6:24-26, must have been current in late seventh-century or early sixth-century Jerusalem. An historical model that places the composition of D and P in the Persian or Hellenistic period lacks consilience with these data and inferences. For this reason, some scholars who date the composition of the Hebrew Bible to these later periods also hold that the Ketef Hinnom inscriptions date to the Hellenistic period. But the late dating of these inscriptions does not withstand scrutiny. By extension the same criticism holds for the late-dating model as a whole. (Ronald Hendel and Jan Joosten, How Old is the Hebrew Bible? A Linguistic, Textual, and Historical Study [New Haven: Yale University Press, 2018], 123-24)
In other words, these amulets are indeed pre-exilic in origin, and, among many other things, a witness that at least some portions of the P source pre-dates the exile, something consistent with the Book of Mormon. For a discussion of this, see Jeff Lindsay, Alleged Problems in the Book of Mormon #4, Including Clashes With Bible Scholarship
For more on these amulets from Ketef Hinnom, as well as a discussion of the evidence for their pre-exilic origin, see:
Jeremy D. Smoak, The Priestly Blessing in Inscription and Scripture: The early history of Numbers 6:24-26 (Oxford, 2015)