Except as otherwise specifically exempted, the tax hereby imposed applies to all tangible personal property purchased from a retailer and located in this City, provided, however, that if the purchaser proves to the satisfaction of the Director of Finance that the property was purchased prior to the effective date of this article, as revised in 1968, or was not purchased for use or consumption in this City and has not been nor will be so used or consumed, the purchaser shall be relieved of liability to pay the tax. (Amended by Ord. No. 136,867, Operative 9/1/68 by Ord. No. 137,011.)