(2) Upon attainment of age sixty-five and upon retirement without completion of twenty-five years of such service, each such member shall receive a pension which together with an annuity which shall be the actuarial equivalent of his accumulated contributions at the time of his retirement and an additional pension which is the actuarial equivalent of the reserve-for-increased-take-home-pay to which he may then be entitled, shall be sufficient to provide him with a retirement allowance equal to one-fiftieth of his final average salary for each year of creditable service in a sheriff's department. Every such member shall also be entitled to an additional pension equal to the pension for any creditable service rendered while not an employee of a sheriff's department as provided under paragraphs three and four of subdivision a of section seventy-five of this article. This latter pension shall not increase the total allowance to more than one-half of his final average salary. For the purpose only of determining the amount of the pension provided in this subdivision, the annuity shall be computed as it would be if it were not reduced by the actuarial equivalent of any outstanding loan, and if it were not increased by the actuarial equivalent of any additional contributions, and if it were not reduced by reason of the member's election to decrease his annuity contributions to the retirement system in order to apply the amount of such reduction in payment of his contributions for old-age and survivors insurance coverage.