39.1. The pension payable to a retirant whose credited service includes service rendered prior to December 29, 1953 shall be not less than the pension portion of the retirement allowance to which he would have been entitled under the former system had the former system been in effect at the time of his retirement plus an annuity which is the actuarial equivalent of his accumulated contributions standing to his credit in the employees’ savings fund of this Retirement Plan at the time of his retirement without offset or deduction of social security benefits he might receive.