(a) Upon any liquidation of a domestic mutual insurer, its assets remaining after discharge of its indebtedness, policy obligations, repayment of contributed or borrowed surplus, if any, and expenses of administration shall be distributed to existing persons who were its members at any time within 12 months immediately preceding the date such liquidation was authorized or ordered or the date of last termination of the insurer's certificate of authority, whichever date is the earlier; except that if the Commissioner has reason to believe that those in charge of the management of the insurer have caused or encouraged the reduction of the members of the insurer in anticipation of liquidation and for the purpose of reducing thereby the number of persons who may be entitled to share in distribution of the insurer's assets, he may enlarge the 12 month qualification period provided for in this subsection by any additional period as he may deem to be reasonable.

(b) The distributive share of each such member shall be in the proportion that the aggregate premiums earned by the insurer on the policies of the member during the combined periods of his membership bear to the aggregate of all premiums earned on the policies of all members. The insurer may and if a life insurer shall make reasonable classifications of its policies held by members and make a formula based upon the classification for determining the equitable distributive shares of each member. Such classification and formula shall be subject to the approval of the Commissioner.