(a) Except as provided in subdivision (b), a local miscellaneous member subject to this article may be retired for service upon his or her written application to the board if he or she has attained age 55 and is credited with five years of service.
(b) Any person who was a member of this system prior to the effective date of the employer’s contract amendment to be subject to this article, and who elects to become subject to this article, may be retired for service upon his or her written application to the board if he or she has attained age 50 and is credited with five years of combined service.