No person, firm or corporation shall use, hold itself out as being, or advertise with the name "industrial bank", except that industrial banks which were properly authorized and doing business on or before June 1, 1967, may use such name at and in connection with their principal office and any branches which were so authorized and doing business on or before said date, and may continue to sell certificates of investment, either fixed or uncertain, and to receive payments in installments or otherwise, with or without an allowance of interest upon such installments, if doing business in such certificates on or before said date.   [PL 1975, c. 500, §1 (NEW).]