This article does not apply to materials which are of a class or kind which are not, or which are manufactured from materials which are not, produced in the United States, nor to key-driven calculators manufactured in branch plants located outside continental United States, but which plants are wholly owned and operated by a corporation the majority of whose stock is owned or controlled by an American manufacturer whose principal manufacturing centers and home offices are located in the United States.
(Amended by Stats. 1955, Ch. 607.)