Section 85A. The commissioner may authorize a mutual fire company, which has and maintains a surplus to policyholders, including any guaranty capital, of not less than the combined capital and surplus provisions required under section forty-eight to issue non-assessable policies, and the provisions of section eighty-one relating to contingent liability of policyholders shall not apply to any such non-assessable policies. Any such mutual fire company shall keep on deposit with the state treasurer the sum of two hundred thousand dollars. Such deposit may be made in the securities and subject to the limitations specified in sections sixty-three and sixty-six, or in cash or such other securities as the commissioner may approve. Any deposit under this section or section ninety-three F, when made with the state treasurer and approved by the commissioner, shall be subject to section one hundred and eighty-five. The commissioner shall allow to the credit of a company in the account of its financial condition all assets deposited with the state treasurer in accordance with the requirements of this section. This section shall not apply to any company unless such company or its predecessor or predecessors, if any, prior to merger or consolidation shall have been actively engaged in the insurance business in one or more states of the United States continuously for ten or more years. A company issuing a non-assessable policy under authority of this section may state therein, or on the filing back thereof, or in both such places, that such policy is non-assessable.