SEC. 4. No person shall, within the limits of the city, wear under his clothes, or concealed about his person, any pistol, revolver, slung-shot, cross-knuckles, knuckles of lead, brass or other metal, or any bowie-knife, razor, billy, dirk, dirk-knife or bowie-knife, or other dangerous weapon. Provided, that this section shall not be so construed as to prevent any United States, State, county, or city officer or officers, or member of the city government, from carrying any any such weapon as may be necessary in the proper discharge of his official duties.