"Belonging to Malkiyahu son of the king "

Malkiyahu is a common Hebrew name.

Jer. 38:6
"Then they took Jeremiah and cast him into the cistern of Malchijah the king's son, which was in the court of the guardhouse; and they let Jeremiah down with ropes Now in the cistern there was no water but only mud, and Jeremiah sank into the mud."

See also Jer. 21:1 = father of Passhur. Compare, 1 Chron 9:12

Avigad, Nahman. Corpus of West Semitic Stamp Seals. (Jerusalem: Israel Academy of Sciences and Humanities, 1997), 55. Seal # 15