Partial excise duty exemption for paper and paperboard limits effective duty and is time bound following rehabilitation recommendation. Exemption under section 5A of the Central Excise Act limits excise duty on paper and paperboard manufactured by Ashok Paper Mills (Bihar Unit) to an amount equal to half the notified rate for a period not exceeding ten years; it applies to goods under Chapter 48 and excludes any value of clearance based exemptions while the notification is in force.