Any society may comply with subsection (a) of Section 11110 by deducting from its surplus an amount which, when added to the reserves on certificates theretofore issued, shall be sufficient to carry such certificates to maturity and establish and maintain after its conversion into a mutual life insurance company a special reserve in such an amount. The basis of such special reserve shall not be altered without the prior written consent of the commissioner. The commissioner shall give such consent only when he finds that such alteration will not impair nor imperil the purpose for which such special reserve is established. Any impairment of such reserve shall, to the extent thereof, be deemed a deficiency of required reserves and shall render the mutual life insurance company insolvent. No part of such special reserve shall be deemed to be a part of the capital paid in or of the surplus of the mutual life insurance company.