If any statements, other than those relating to age, sex, and identity, are required as a condition to issuing such an annuity or pure endowment contract, and subject to section 968 of this title, there shall be a provision that the contract shall be incontestable after it has been in force during the lifetime of the person or of each of the persons as to whom such statements are required, for a period of two years from its date of issue, except for nonpayment of stipulated payments to the insurer; and at the option of the insurer, such contract may also except any provisions relative to benefits in the event of total and permanent disability and any provisions which grant insurance specifically against death by accident.