It is unlawful for any person to manufacture, mix, compound, sell or offer for sale, for human consumption in this state, flour as defined in section one of this article, unless the following vitamins and minerals are contained in each pound of such flour: Not less than two and not more than two and five-tenths milligrams of thiamine; not less than one and two-tenths and not more than one and five-tenths milligrams of riboflavin; not less than sixteen and not more than twenty milligrams of niacin or niacinamide; not less than thirteen and not more than sixteen and five-tenths milligrams of iron; except in the case of self-rising flour which in addition to the above ingredients shall contain not less than five hundred and not more than fifteen hundred milligrams of calcium: Provided, That the provisions of this section do not apply to flour sold to distributors, bakers or other processors, if the purchaser furnishes to the seller a certificate in such form as the commissioner has prescribed by rule, certifying that such flour will be: (1) Resold to a distributor, baker or other processor; (2) used in the manufacture, mixing or compounding of flour, white bread or rolls enriched to meet the requirements of this article; or (3) used in the manufacture of products other than flour, white bread or rolls. It is unlawful for any such purchaser furnishing any such certificate to use or resell the flour purchased in any manner other than as prescribed in this section: Provided, however, That the provisions of this section do not apply to noncommercial flour manufactured by small flour mills, located in this state, for persons from wheat harvested in this state or to any other flour produced and sold at retail by such mills.