In every county coming under the provisions of

Section 31676.1 subsequent to January 1, 1953, every current service pension and prior service pension payable for time commencing on the effective date of this

section to any member who was retired prior to said effective date by reason of having attained the age of compulsory retirement, is hereby increased to the amount it would be if the provisions of this chapter, including Sections 31676.1 and 31760.1, as they existed on the date that

Section 31676.1 became applicable to the members’ retirement system, had been in effect on the date of the actual retirement of the member; but this

section does not authorize any decrease in any such pension, nor does this

section give any such retired member, or his successors in interest, any claim against the county or district for any increase in any pension paid or payable for time prior to its effective date. Calculations of pensions under this

section shall be made on the basis of current interest rate and mortality tables. This

section shall not apply to any retirement system established under the provisions of this chapter, nor to the members or retired members of any such system unless and until the governing board of the county or district covered by such retirement system elects to be subject to the provisions of this

section in the manner provided by

Article of this

chapter with respect to the establishment of a retirement system hereunder; except that an election among the employees is not required.