No person except a parent or guardian shall purchase from, sell, exchange, give, lend or furnish to any person under the age of 18 years a revolver or pistol of any description, shotgun or rifle which may be used for the explosion of cartridges or any air gun, "B-B gun," gas operated or spring gun or any ammunition therefor or any knife or knives having the appearance of a pocket knife, the blade or blades of which can be opened by a flick of a button, pressure on the handle or any mechanical devices; or any instrument, toy or weapon commonly known as a "slingshot," or any bow made for the purpose of throwing or projecting missiles for any kind by any means whatsoever, whether such instrument is called by any name set forth above or by any other name.
(`78 Code, § 9.50.010.)