Homer's Reference to Writing in Proitos' Era

In Book VI of the Iliad Homer refers to a letter written by Proitos, king of Tiryns, and ad dressed to his father-in-law, Iobates, king of Lycia, requesting him to kill Bellerophontes. Proitos entrusts the closed, folded letter to Bellerophontes himself, so that he would show it to Iobates. But in which script was that message written by Proitos? If we accept the genealogies of the his toric tradition, then Proitos must have lived in the Mycenaean era and so he wrote in linear B. If, however, we connect him with the Hellenikon or the Ligourio pyramid, accepting the tradition mentioned by Pausanias (Corint. 25,7), then, according to the dating of these pyramids through the optical thermoluminescence method, Proitos wrote in hieroglyphics (to better determine the relative time-span, excavation data from Argolid and other places are co-evaluated). These hiero glyphics are Cretan hieroglyphics, from which the linear scripts A, B and the Cypriot syllabic script originate.