§ 1309. If any person shall carry concealed a deadly weapon upon or about his person, other than an ordinary pocket knife, or shall sell such weapon to a minor other than an ordinary pocket knife, such person shall, upon conviction, be fined . . . § 1313. Carrying concealed deadly weapons shall be lawful in the following cases: By sheriffs, constables, marshals, policemen, and other ministerial officers, when necessary for their protection in the discharge of their official duties, by United States mail carriers when actually engaged in their dutes as such, and by agents and messengers of express companies when neccessary for their protection in the discharge of their official duties.