That Notification says: "The Central Government has exempted goods falling 327 under Item No. 68 of the First Schedule to the (1 of 1944), cleared from the factory of manufac ture, on sale, from so much of the duty of excise leviable thereon as is in excess of the duty calculated on the basis of the invoice price (excluding duty and local taxes, if any, included in such price) charged by the manu facturer for the sale of such goods: Provided that the aforesaid exemp tion shall be admissible only if (i) the manufacturer files with the Superin tendent of Central Excise having jurisdiction a written declaration to the effect that he opts to avail of the said exemption: (ii) Omitted as unnecessary (iii) (iv) the invoice price is not influenced by any commercial, financial or other relation ship whether by contract or otherwise between the manufacturer or any person associated in business with the manufacturer and the buyer other than the relationship created by sale of the aforesaid goods: (v) Omitted as unnecessary.