Upon the liquidation of a domestic reciprocal insurer, its assets remaining after discharge of its indebtedness and policy obligations, the return of any contribution of the attorney to its surplus made as provided in RCW 48.10.190, and the return of any unused deposits, savings, or credits, shall be distributed to its subscribers who were such within the twelve months prior to the last termination of its certificate of authority according to such formula as may have been approved by the commissioner.