Policies may be issued in this state providing for not more than 1 year preliminary term insurance by the incorporation therein of a clause on the face of the policy distinctly specifying that the first year’s insurance is term insurance. If the premium charged for term insurance under a limited payment life preliminary term policy providing for the payment of all premiums thereon in less than 20 years from the date of the policy, or under an endowment preliminary term policy, exceeds that charged for life insurance under 20 pay life preliminary term policies of the same insurer at the same age, the reserve thereon at the end of any year, including the first, shall not be less than the reserve on a 20 pay life preliminary term policy issued in the same year and at the same age, together with an amount which shall be equivalent to the accumulation of a net level premium sufficient to provide for a pure endowment at the end of the premium payment period equal to the difference between the value at the end of such period for such 20 pay life preliminary term policy and the full reserve at such time of such a limited payment life or endowment policy: Provided, That this section shall apply to all policies issued subsequent to January 1, 1930, and prior to the operative date of section 4060 (standard nonforfeiture law).