For the purpose of this chapter "junk dealer" means all persons, firms or corporations engaged in the business of purchasing or selling secondhand, or castoff material of any kind, such as old iron, copper, brass, lead, zinc, tin, steel, aluminum, and other metals, metallic cables, wires, ropes, cordage, bottles, bagging, rags, rubber, paper, and other like materials. (1991 Code § 5.20.010, as amended)