The 40th Shield

The Shield of the 40th Armor/Cavalry is more symbolic of the regiment rather than a story of historical events.

The T Rex represents Armor because of its scaley hide

The Sword is Excalibur of King Arthur fame.

I think the lizard tounge of blue is a reference to the Great Seal of America and so is the light of God around the Sword. The one eye only also makes me think this another reference to the Great Seal.

Armor guards the gold at Fort Knox but this unit never held this as far as I know.