The certificate relieves the seller from the burden of proof only if taken in good faith from a person who is engaged in the business of selling tangible personal property and who holds the permit provided for in sections 3.08.035 to 3.08.090, inclusive, of this chapter and who, at the time of purchasing the tangible personal property, intends to sell it in the regular course of business or is unable to ascertain at the time of purchase whether the property will be sold or will be used for some other purpose. (MC Ord. 39A §31, 1971)