Special duty of customs imposed as an additional charge on specified tariff duties; limited duration with transitional effect. A statutory provision imposes a special duty of customs as an addition to the total customs duty chargeable under the Tariff schedule, computed on goods specified in the First Schedule or as amended or notified, with a proviso excluding certain duties from the computation. The levy is time limited and ceases after a specified terminal date, with transitional effect preserved for acts or omissions before that cesser and application of the General Clauses Act to treat the cessation as if repealed by subsequent legislation.