Figure 8 shields

[Dan Howard]

Internal grip and baldric were used by the warrior to properly handle the shield.

They probably didn't have a hand grip. Illustrations suggest that they were wielded solely by means of a shield strap. Herodotus says the same thing.
He also says that the first shields with handgrips were used by the Carians. The first handgrips likely coincide with the first shields that had central shield bosses near the end of the Bronze Age.