"There is no reason to think that when Gildas says all the coloniae were laid low by battering rams during the Saxon revolt he did not mean precisely what he wrote."
-Christopher Gidlow, Revealing King Arthur

Since you can't find a gate destroyed by a battering ram (wood would completely disintegrate after 50 years, never mind 1600) you say Gildas is wrong?

Look at the plate of Valentinian (scroll down) http://real.mtak.hu/49949/1/MravZs_Torques_in...OkCs_u.pdf There's crested helmets like in the Vergilius Romanus manuscript. That sword looks like it might have a long hilt.

On second thought it's probably just a normal migration sword. It's the helmets that are interesting. Seeing these crests on late roman soldiers does add some authenticity to the manuscript.