Retirement of a member for service shall be made by the retirement board as follows:
(1) Any judge who, on August 9, 1971 or within one year thereafter, shall have completed as a judge the years of actual service required under chapter
2.12 RCW and who shall elect to become a member of this system, shall in all respects be deemed qualified to retire under this retirement system upon the member's written request.
(2) Any member who has completed fifteen or more years of service may be retired upon the member's written request but shall not be eligible to receive a retirement allowance until the member attains the age of sixty years.
(3) Any member who attains the age of seventy-five years shall be retired at the end of the calendar year in which the member attains such age.
(4) Any judge who involuntarily leaves service or who is appointed to a position as a federal judge or federal magistrate at any time after having served an aggregate of twelve years shall be eligible to a partial retirement allowance computed according to RCW
2.10.110 and shall receive this allowance upon the attainment of the age of sixty years and fifteen years after the beginning of the member's judicial service.