of this title shall not apply to
(1) any common carrier or contract carrier, with respect to any switchblade knife shipped, transported, or delivered for shipment in interstate commerce in the ordinary course of business;
(2) the manufacture, sale, transportation, distribution, possession, or introduction into interstate commerce, of switchblade knives pursuant to contract with the Armed Forces;
(3) the Armed Forces or any member or employee thereof acting in the performance of his duty; or
(4) the possession, and transportation upon his person, of any switchblade knife with a blade three inches or less in length by any individual who has only one arm.