Technical meaning of "alkyd resins" governs exemption, and later definitional amendment cannot be applied retrospectively.

Where an exemption notification uses the undefined technical term "alkyd resins", the expression must be construed in its technical sense for the relevant period. On the material placed before the Tribunal, the products Polylite 8001 and Polylite 93-410 were treated as falling within the broader class of alkyd resins, so they qualified for exemption under Notification No. 156/65. The later explanation introduced by Notification No. 122/71 could not be applied retrospectively to the earlier period to deny that exemption, particularly where the technical literature supported inclusion of polyester resins within alkyd resins. The duty demand therefore failed.

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Issues: (i) whether the products Polylite 8001 and Polylite 93-410 were "alkyd resins" within Notification No. 156/65 so as to qualify for exemption from excise duty; (ii) whether the explanation introduced in Notification No. 122/71 could be applied to the earlier period to deny the exemption.

Issue (i): whether the products Polylite 8001 and Polylite 93-410 were "alkyd resins" within Notification No. 156/65 so as to qualify for exemption from excise duty.

Analysis: The Notification in force during the material period did not define "alkyd resins", so the expression had to be understood in its technical sense. The technical literature placed before the Tribunal showed that polyester resins are included within the broader class of alkyd resins, and the Chemical Examiner himself had stated that the dividing line between polyester resins and alkyds was not sharp. On that basis, the earlier classification of the products as alkyd resins was accepted as consistent with technical understanding.

Conclusion: The products Polylite 8001 and Polylite 93-410 were alkyd resins and were entitled to the exemption under Notification No. 156/65.

Issue (ii): whether the explanation introduced in Notification No. 122/71 could be applied to the earlier period to deny the exemption.

Analysis: The explanation defining "alkyd resins" was introduced only on 1-6-1971. There was no corresponding definition in the earlier notification or in the technical material relied upon, and the later definition could not be used to operate against the assessee for the prior period, particularly where the technical literature supported inclusion of polyester resins within alkyd resins.

Conclusion: The explanation in Notification No. 122/71 could not be applied retrospectively to the earlier period to the disadvantage of the assessee.

Final Conclusion: The demand for duty failed because the goods were treated as exempt alkyd resins for the relevant period, and the later definitional notification could not govern the prior clearances.

Ratio Decidendi: Where an exemption notification uses an undefined technical expression, the expression must be construed in accordance with technical understanding during the relevant period, and a later definitional amendment cannot be applied retrospectively to deprive the assessee of the exemption.

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