In Section 31641.2 compensation first earnable shall be that earnable by the member at the time of the commencement of his membership in the retirement system, except that if a member who, prior to January 1, 1952, was a member of any retirement system in the same county which was superseded by a system established under this act, if such member so requests, the compensation first earnable by him at the later of the following times shall be used:
(a)
The commencement of his membership in such superseded retirement system.(b)
The date on which this retirement system first became operative.
Source:
Section 31641.3, https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV§ionNum=31641.3..