"Photo #14. PzIII with screens after being shot in the side by 15P-II and RKS anti-tank rifles."
"Photo #15. Side. Armour thickness: 30 mm. 15P-II anti-tank rifle, OKB-44 bullets.1 and 2: range of 100 meters. Dents in the main armour after penetrating the 5 mm armour screen."
As you can see, this measure was very effective against rifles. However, by the time these armour screens were introduced, the original reason for anti-tank rifles (to supplement losses of light anti-tank guns) was remedied, and infantry units could face enemy tanks with 45 mm cannons, which were unaffected by 5 mm screens.