87.140.  Administration vested in board of trustees — how appointed — vacancies — compensation — oath — voting — board members may serve as trustees for other pension plans. — 1.  The general administration and the responsibility for the proper operation of the retirement system shall be vested in a board of trustees of nine persons.  The board shall be constituted as follows:

  (1)  The chief of the fire department of the city, ex officio;

  (2)  The comptroller or deputy comptroller of the city, ex officio;

  (3)  Two members to be appointed by the mayor of the city to serve for a term of two years;

  (4)  Three members to be elected by the members of the retirement system for a term of three years who shall be members of the system and hold office only while members of the system;

  (5)  Two members who shall be retired firemen to be elected by the retired firemen of the city and who shall hold office for a term of three years.

  2.  If a vacancy occurs in the office of trustee, the vacancy shall be filled for the unexpired term in the same manner as the office was previously filled.

  3.  The trustees shall serve without compensation, but they shall be reimbursed from the expense fund for all necessary expenses which they may incur through service on the board.

  4.  Each trustee shall, within ten days after his appointment or election, take an oath of office before the clerk of circuit court of the city, that, so far as it devolves upon him, he will diligently and honestly administer the affairs of the board and that he will not knowingly violate or willingly permit to be violated any of the provisions of the law applicable to the retirement system.  The oath shall be subscribed to by the member making it and certified by the clerk of circuit court and filed in his office.

  5.  Each trustee shall be entitled to one vote on the board. Five votes shall be necessary for a decision by the trustees at any meeting of the board.

  6.  Notwithstanding any provision of sections 87.120 to 87.371 to the contrary, the board of trustees of the retirement system shall not be prevented from simultaneously acting as the trustees of any other pension plan that provides retirement, disability, and death benefits for firefighters employed by any city not within a county and the firefighters'^* covered dependents.  The administration of the other pension plan shall be in accordance with the terms of such pension plan.  Nothing in this subsection shall prevent the board of aldermen^** of a city not within a county from adopting ordinances to govern the pensioning of firefighters and such firefighters'^* covered dependents in any other pension plan simultaneously administered by the board of trustees of the retirement system.