Shephelah clay was used in the production of the Early Persian lion stamp-impressed jars (Lipschits, p. 63, see here for distribution map). Shephelah clay only occurs in the three Shephelah districts of Joshua 15. The Early Persian province of Yehud’s border with the provinces of Ashdod and the Idumean wilderness seems to have extended in a rough line from Aijalon to Keilah. Since the Persian administrative center in Yehud was at Ramat Rahel, it makes sense to place the location of the gathering of the lion-impressed jar clay between Adullam and Eshtaol, possibly at Zanoah, Socoh, or, somewhat less likely, Eshtaol. Shephelah clay was also apparently used to make post-701 BC lmlk-stamped jars, even though the Shephelah was devastated by Sennacherib’s campaign. My question is, why is Shephelah clay used for the production of Judahite stamped jars even in periods the Shephelah is not an important part of Judah, such as the early Persian period and the early 7th C BC?