Special customs duty imposed as an additional levy on tariff-based customs charges, excluding specified duties, with temporary application. A special duty of customs operates as an addition to customs charged under the First Schedule to the Tariff Act or that Schedule as amended or read with an applicable notification, fixed at an additional levy equal to ten per cent of the total customs amount so chargeable, with the proviso that duties under specified provisions are excluded from the computation; the provision is subject to an express cessation date and transitional saving for prior acts or omissions.