Exemption from excess excise duty on paper with majority unconventional raw materials where higher duty was not levied during specified period. The Government recognized a prevailing practice that excise duty on paper and paperboard containing at least 50% unconventional raw materials was not levied in excess of 15% ad valorem during 16-19 March 1995, and directed-under statutory powers-that any duty above 15% ad valorem need not be paid for such products where the higher duty was not levied during that specified period in accordance with the practice.