Jamieson, Fausset and Brown on Revelation 9:7

7. prepared unto battle--Greek, "made ready unto war." Compare Note, see on Joe 2:4, where the resemblance of locusts to horses is traced: the plates of a horse armed for battle are an image on a larger scale of the outer shell of the locust.

crowns--(Na 3:17). Elliott explains this of the turbans of Mohammedans. But how could turbans be "like gold?" Alford understands it of the head of the locusts actually ending in a crown-shaped fillet which resembled gold in its material.

as the faces of men--The "as" seems to imply the locusts here do not mean men. At the same time they are not natural locusts, for these do not sting men (Re 9:5). They must be supernatural.