Section 13-248. Retirement; selection of age fifty-five

Any person becoming
  a member who was not previously a member or who during his or  her  last
  previous  membership  in  the pension fund contributed on the basis of a
  minimum  retirement  age  of  fifty-five,  may  elect,  prior   to   the
  certification  of  his or her rate of contribution, to contribute on the
  basis of a minimum retirement age of fifty-five by  a  written  election
  duly executed and acknowledged and filed with the board. The minimum age
  of  retirement  for  such members so electing shall be fifty-five years,
  and all contributions and benefits payable by  or  on  account  of  such
  member shall be computed on the basis of such minimum retirement age.