(a) Since he last became a member, and

(b) Prior to the completion of twenty years of total service in such department, and

(c) Toward which he and his employer have contributed under this section, plus 4. An additional pension, if required, of such amount as shall be necessary to increase the total amount of the benefits provided under paragraphs one, two and three of this subdivision e to at least one-half of his final average salary. The computation of this pension shall be limited so that the total service in such department used as a basis for pension credit under this paragraph four and paragraph three of this subdivision e, shall not exceed twenty years, plus 5. An additional pension equal to the pension for any creditable service rendered while not an employee of such department as provided under paragraphs three and four of subdivision (a) of section three hundred seventy-five of this article. This pension shall be based on member's final average salary, and

(a) Be payable only if such member has attained age sixty-two at the time of retirement and has not completed twenty years of service in such department for which he receives credit under this article, and

(b) Not increase the total allowance to more than he would have received had his total service been rendered in such department. 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 survivors insurance coverage. f. A member who elects or is required to contribute in accordance with this section shall retire on the first day of the calendar month next succeeding his attainment of age sixty-two. g. The increased pensions to any member in such department, as provided by this section, shall be paid from additional contributions made by the appropriate participating employer on account of such member. The actuary of the retirement system shall compute the additional contributions for each member who elects the special benefits provided under this section. Such additional contributions shall be computed on the basis of contributions during the prospective service of such member which will cover the liability of the retirement system for such extra pensions. Upon approval of the comptroller, such additional contributions shall be certified by him to the fiscal officer of the participating employer. The amount thereof shall be included in the annual appropriation of the participating employer for its police department. Such amount shall be paid on the warrant of the fiscal officer of the participating employer to the pension accumulation fund of the retirement system. h. In computing the twenty years of completed service of a member in the police department, full credit shall be given and full allowance shall be made for service of such member in time of war and service with the American expeditionary forces subsequent to November eleventh, nineteen hundred eighteen, and prior to June thirtieth, nineteen hundred nineteen, of honorably discharged officers, soldiers, sailors, marines and army nurses, who were actual residents of the state at the time of their entry into the military service of the United States, and the service of members of the national guard in the military service of the United States of America pursuant to the call of the president for Mexican border service. i. The provisions of this section shall be controlling, notwithstanding any provision in this article to the contrary.