Hi folks,
this ignorant fly fly boy would like to know what the these items are:
On M1 's front armor of turret. Many pictures show, what looks like a rectangular
frame item with corner markings, both sides of barrel, what it is?
On side & back of turret there are horisontally louvered metal pieces- is this some sort of anti RPG protection?

Moved this to the correct section.

Probably reactive armor; when it is hit by a projectile it explodes outward, preventing damage to the tank's base armor.