For the purpose of this chapter an insurance company may be incorporated as a stock insurer with its capital divided into shares and owned by the stockholders, or a mutual insurer without capital stock the governing body of which is elected by its policyholders. There shall be not less than 15 incorporators of whom not less than two-thirds shall be citizens of this State. Except as provided in sections 4831 through 4856 of this title, no unincorporated association shall be formed after July 1, 1968, for the purpose of doing any insurance business in Vermont. Those domestic unincorporated associations which are doing insurance business of any kind under authority of the Commissioner on July 1, 1968, may continue to carry on their business subject to the provisions of this part. (Added 1967, No. 344 (Adj. Sess.), § 1 (ch. 1, subch. 1, § 2); amended 1971, No. 31, § 2, eff. March 31, 1971.)