Persons who are officers and employees of this City and County on January 8, 1932, shall become members of the Retirement System subject only to the following provisions, in addition to the provisions contained in Sections 3.670, 3.672, 8.500, 8.510, 8.511, 8.520, 8.525 and 8.560, of this Charter.
(a) The system shall be applied to such offices, departments, bureaus, or classes of officers or employees of the City and County, including teachers in the San Francisco school department, as the supervisors shall determine; provided, however, that the contributions to be made by said teachers and the benefits to be received by said teachers under said Retirement System shall be based upon the proportion of salaries of said teachers which have been and shall be paid out of funds contributed by the City and County, excluding therefrom the portion of such salaries which have been or shall be paid out of funds contributed by the State of California; and in determining such proportion it shall be taken to be the same proportion which the whole amount of money contributed by the City and County to the common school fund in any fiscal year bears to the whole amount of money contributed to such fund in such year by the state and by the City and County; and provided, further, that nothing herein contained shall be construed to deprive any teacher of the right to receive benefits under any pension or Retirement System now or hereafter established by the State of California.
(b) No member of the Retirement System shall be retired, except in case of disability incapacitating him for the performance of his duties, unless he shall have attained the age of 62 years and completed 10 years of continuous service, but retirement shall be compulsory at the age of 70 years. It may be provided, however, under such Retirement System, that members may retire after 30 years of continuous service; the benefits at retirement in such cases to be determined, because of retirement at an age below 62, in accordance with the tables recommended by the actuary and approved by said retirement board.
(c) All persons who were retired prior to October 1, 1925, from service as teachers in the public schools of San Francisco, under the provisions of the law of 1913, establishing the California Public School Teachers' Retirement Salary Fund, shall be entitled to and shall receive retirement allowances, to be calculated on the same basis as that established for determining the retirement allowances provided for members of the said Retirement System.