(a) No person shall carry on or about his person a pistol, a knife having a blade two and one-half inches in length or longer, “brass” knuckles, a billy or any other dangerous weapon. However, upon the trial of this charge, the defendant shall be acquitted if it appears that he was at the time engaged in a lawful business, calling, employment or occupation and that the circumstances in which he was placed justified a prudent man in possessing such a weapon for the defense of his person or family.
(b) Whoever violates this section is guilty of a misdemeanor of the third degree.