Central excise exemption amendment updates ad valorem duty entries for specified tariff items, altering prior notification entries. Amendment substitutes the entry in column (4) for S. No. 17 and for S. No. 34 in Notification No. 132/86-Central Excises with a uniform ad valorem duty rate, effected under the rule-making authority of the Central Excise Rules by Notification No. 171/87-C.E.