Tear-gas gun, most likely; they’re very common all over central Europe. No permit, no license, shoots tear-gas cartridges. You can carry them anywhere.
Like this: http://shop.ehobbyasia.com/media/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/T/K/TKW-REV-M29HW-SVJF_1_mark.jpg
interesting
