If the Center director is not satisfied with the results of any test provided for in § 151.71 or § 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 Center 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.