If title II of the Social Security Act [
42 U.S.C.
401 et seq.] is amended at any time after December 31, 1974, to reduce the eligibility requirements for old-age insurance benefits, disability insurance benefits, wife’s insurance benefits payable to a wife, husband’s insurance benefits, child’s insurance benefits payable to a child of a deceased individual, widow’s insurance benefits payable to a widow, widower’s insurance benefits, mother’s insurance benefits payable to a widow, or parent’s insurance benefits, such reduced eligibility requirements shall be applicable, in accordance with regulations prescribed by the Board, to individuals, spouses, or survivors, as the case may be, under section
231a of this title to the extent that such reduced eligibility requirements would provide such individuals, spouses, or survivors with entitlement to annuities under such section
231a of this title to which they would not be entitled except for such reduced eligibility requirements: Provided, however, That no annuity shall be paid to any person pursuant to the provisions of this subsection if that person does not satisfy an eligibility requirement imposed by section
231a of this title of a kind not imposed by the Social Security Act [
42 U.S.C.
301 et seq.] on December 31, 1974, or an eligibility requirement imposed by section
231a of this title of a kind which was imposed by the Social Security Act on December 31, 1974, but which was not reduced by the amendment to that Act: Provided further, That the annuity amounts to which such individuals, spouses, or survivors will be entitled under this subchapter by reason of the provisions of this subsection shall be only such amounts as are determined under the provisions of section
231b
(a),
231c
(a), or
231c
(f), respectively, of this title.