Polish AT-rifle WZ.35
Anti-tank rifle, model 35 - Wikipedia, the free encyclopedia
The weapon was initially a top secret of the Polish Army, and was also known by various codenames. Until mobilization in 1939, the combat-ready rifles were held in closed crates enigmatically marked, "Do not open; surveillance equipment."
After the fall of Poland, the German army captured large numbers of the kb ppanc wz.35 and used it as "Panzerbüchse 35 (polnisch)" (abbreviated "PzB 35(p)"). The Italian army also benefitted from the booty and used it under its own designation as "fucile controcarro 35(P)." Both names translate roughly as "Anti-tank Rifle 35 (Polish)."
Maroszek WZ 35, polish secret weapon - WW2inColor Talk