(i)Where the Chief Controlling Revenue Authority or Superintendent of Stamps authorised by him in this behalf is, having regard to the number of instruments executed by a person and the amount of duty charged thereon, satisfied that it is necessary in the public interest so to do, it or he may by an order in writing, authorise such person to use franking machine subject to such conditions as laid by general or special order in this behalf by the Chief Controlling Revenue Authority.