Everybody knows the famous Panzerschreck but what everybody doesn't know is, firing this beast can actually burn your face. 
The projectile was using highly imflamable and corrosive explosives to be launched. This is the reason why a big shield is place between the nozzle and the shooter. To be able to see where you were shooting a heavy glass window is cutted on the shield. These rare glass are spare ones which goes in a little box attached to the shield.