Upon the liquidation of a domestic reciprocal insurer, its assets remaining after discharge of its indebtedness and policy obligations, the return of any contributions of the attorney or other persons to its surplus made as provided in section twenty- three of this article, and the return of any unused premium, savings, or credits then standing on subscribers' accounts, shall be distributed to its subscribers who were such within the twelve months prior to the last termination of its license, according to such reasonable formula as the commissioner may approve.