If the port director is not satisfied with the results of any test provided for in Sec. 151.71 or Sec. 151.73, he may, within 14 calendar days after receiving the report of the results of such test, proceed to have another test made upon a suitable sample of the wool or hair at the expense of the Government. When the port director is proceeding to have another test made, he shall, within the 14-day period specified in this paragraph, notify the importer by mail of that fact.