Section 13-639. Board of estimate; authority to recommend retirement

Any
  officer, whether appointed or elected, clerk or employee of  any  agency
  in  the  employ of the city or of any of the municipalities, counties or
  parts thereof which  have  been  incorporated  into  the  city  and  any
  officer,  clerk  or  employee  whose  salary or compensation is a county
  charge who shall have been employed for a period  of  thirty  years  and
  upwards  and  who shall have become physically or mentally incapacitated
  for the further performance of the duties of his or her position, may be
  recommended for retirement from active service to the board of  estimate
  by  any  member thereof whenever, in his or her judgment, it shall be to
  the interest of the public service. The term of service, however,  shall
  not  be  affected  by  any  change  in  title,  duty or salary or by any
  promotion or by a vacation or leave  of  absence  or  by  any  temporary
  disability by reason of sickness or accident or by any transfer from one
  agency  to another during the period of service, or by any change of any
  of the agencies in which service  shall  have  been  performed  from  an
  office paid by fees to a salaried office.