sqaure tabs on helmets

[m1steelpot]

What are these square tabs on the back of some of the Marines helmets? Here is one of the pics.
www.loudounmarines.org/images/572_InchonSeaWall2.jpg
Are they a sign of a beach master or are they like the illumination disks the airborne troops had in WWII?

[pop401k]

Illumination is one option. another might be for rank status. In the photo I notice both vertical and horizontal tabs. On D-Day 1944, officers wore vertical painted strips, NCOs horizontal.

[m1steelpot]

That could be the more logical answer. As i do notice the vertical and horizontal now. Interesting they would use this concept again if in fact that is the reason. I wonder if its a piece of cloth cut into squares and pinned on or something.