Section 93C. Any mutual company formed or authorized to transact business under the third, fifth, sixth, seventh, eighth, ninth, tenth, twelfth or thirteenth clause of section forty-seven or under clause (b), (c) or (d) of section forty-eight A may, except as provided in sections ninety B and ninety-three, at any time establish a guaranty capital as provided in and subject to the provisions of section seventy-nine.