Again, an emblem of the Allied invasion, the Invasion Arm US Flag. 
Used in many airborne operations, Normandy, South of France, Holland ...
Seen on original pictures of 101st and 82nd Airborne Units, this armband was sometimes cut and adapted to uniforms and camouflages. 
This reproduction item is clearly the best we have seen, same fabric, same size and same design as originals. 
With a bit of weathering, it would be a must for reenactors !