Any person, firm, retail dealer, wholesale dealer, pawnbroker, or corporation who shall sell, dispose of, or offer for sale or cause or permit to be sold, disposed of, or offered for sale any pistol, revolver, or short-barreled firearm of less than 15 inches in length, whether the same shall be his own property or whether he shall sell the same as an agent or employee of another, shall obtain from the department a license permitting the sale of such pistols, revolvers, and firearms. Nothing in this chapter shall apply to or prohibit the casual sales of the articles referred to in this Code section between individuals or bona fide gun collectors.