Retrospective applicability of customs notification affirmed, treating the notification as effective from an earlier commencement date. Deeming provision declares that the Government notification issued under sub section (1) of section 25 of the Customs Act, read with sub section (12) of section 3 of the Customs Tariff Act, is to be treated as having come into force from an earlier date, thereby conferring retrospective effect on the notification and validating its legal operation from that deemed commencement for all purposes.