Notwithstanding the provisions of this subchapter, if any person or firm engaged in the business on January 1, 1977, of servicing portable fire extinguishers, installing or servicing fixed fire protection systems, or performing hydrostatic testing of fire extinguishers derived twenty-five percent (25%) or more of the personal or firm income from servicing portable fire extinguishers or installing or servicing fixed fire protection systems or hydrostatic testing of fire extinguishers during the 1976 calendar year, the person or firm shall be registered or issued a license to continue in the business upon payment of the annual registration or license fee prescribed in this subchapter for the particular type of business, if the applicant's qualifications meet those requirements established by the Arkansas Fire Protection Licensing Board.