(1) Service increment shall be the sum obtained by computing the number of whole years in excess of twenty years during which a contributor has been employed by such city or county and paid out of the city treasury and multiplying the said number of years so computed by an amount equal to one-fortieth of the pension which has become payable to such contributor in accordance with the provisions of this act: Provided, That no service increment may be paid for employment of more than twenty such excess years nor for any excess years which shall accrue after a contributor has reached the age of seventy years and no service increment shall be paid in excess of one hundred dollars ($100.00) per month.

(2) Each contributor, from and after the effective date of¹ this amendment, shall pay into the board of pensions a monthly sum, in addition to his or her pension contribution, which shall be equal to one-half of one per centum of his or her salary: Provided, That such payment shall not exceed the sum of one dollar ($1.00) per month nor shall the total payment for pension contribution and service increment contribution exceed thirteen dollars ($13.00) per month: And Provided, That such service increment contribution shall not be paid after a contributor has reached the age of sixty-five years.

(3) Persons who are pension fund contributions on the effective date of this amendment who have already reached the age of sixty-five years shall have his or her service increment computed on the years of employment prior to the date of reaching his or her sixty-fifth birthday.

(4) Any pension fund contributor who shall, after the effective date of this act, leave the service of such city or county after having completed at least twenty years' service but before reaching the age of sixty years and who shall continue to pay pension contributions into the pension fund, shall not pay service increment contributions after the date of leaving the service of such city or county and shall have his or her service increment limited to the actual years spent in the service of such city or county.

(5) Service increment contributions shall be paid at the same time and in the same manner as pension contributions and may be withdrawn in full, without interest, by persons who leave the employment of such city or county, subject to the same conditions by which pension contributions may be withdrawn. When any person is re-employed by the city or county after withdrawal of pension contributions, his or her prior service shall not be used in the computation of service increment unless the amount of such contributions be repaid into the pension fund, subject to the same conditions by which pension fund withdrawals are permitted to be repaid.

(6) All employes of such city or county who are now contributors to the pension fund, and all persons who are employed by such city and county after the effective date of this amendment who are required to become contributors to the pension fund, shall be subject to the provisions of this amendment.