Notwithstanding any other provision contained in this chapter, all members of the fire pension fund who became members of such system prior to June 16, 1944 and have heretofore or are hereafter retired pursuant to Sections 4.20.070, A 2 through A 6; 4.20.080, A 3 through A 5; 4.20.090 C through F or Section 4.20.150, as provided in said sections on and after April 8, 1954 or who elect under Section 4.20.140 to receive the service retirement benefits    provided by said Section 4.20.070 A 3 through A 6, as provided in said section on and after April 8, 1954, shall be entitled to a pension based upon the average salary attached to the respective rank or ranks held during the three years immediately preceding the date of retirement, such pension to increase or decrease as salaries attached to the respective rank or ranks are increased or decreased. The provisions of this section shall not apply to pension payments made prior to January 9, 1958. (Ord. 3608-NS (part), 1958: Ord. 2188-NS § 16.2, 1938)