The Mayor and City Council when authorized by a majority vote of the qualified electors of the city, are hereby empowered and authorized to exempt from City taxation for a period not to exceed five (5) years, manufacturing establishments and public utilities as an inducement to their locating in the City; provided, however, the provisions of this section shall not apply to manufacturing establishments and public utilities located in the City on the date of the approval of this Charter by the Governor of the State.