Exemption for cut and polished diamond imports under Section 28A applies where authorised laboratory offices validate eligibility. Exemption under Section 28A of the Customs Act applies to imports of cut and polished diamonds effected by authorised agencies/offices of the laboratories referenced in the Handbook of Procedure; the exemption is conditioned on validation by those authorised laboratory offices and is the subject of Notification No. 21/2017-Customs circulated for guidance to importers, clearing agents and the trading public.