The following persons shall not be required but may obtain licenses as public weighmasters: (1) a government weights and measures officer when acting within the scope of his official duties; (2) a person weighing property, produce, commodities or articles that he or his employer, if any, is either buying or selling; and (3) a person weighing property, produce, commodities or articles in conformity with the requirements of Federal statutes or the statutes of this Territory relative to warehousemen or processors.