Adam Clarke on Job 19:24

Iron pen and lead - Some suppose that the meaning of this place is this: the iron pen is the chisel by which the letters were to be deeply cut in the stone or rock; and the lead was melted into those cavities in order to preserve the engraving distinct. But this is not so natural a supposition as what is stated above; that Job refers to the different kinds of writing or perpetuating public events, used in his time: and the quotations from Pliny and Pausanias confirm the opinion already expressed.