31727. The non-service-connected disability retirement pension shall be such an amount as with that portion of his annuity provided by his accumulated normal contributions will make his disability retirement allowance, exclusive of the annuity provided by his accumulated additional contributions, equal:(a) Ninety percent of one-sixtieth of his final compensation multiplied by the number of years of service credited to him, if (1) the member must rely upon service in another retirement system in order to be eligible to retire or (2) such disability retirement allowance exceeds one-third of his final compensation.(b) If the member is eligible to retire without relying upon service in another retirement system, and the disability retirement allowance computed under (a) does not exceed one-third of his final compensation, 90 percent of one-sixtieth of his final compensation multiplied by the number of years of service which would be creditable to him were his service to continue until attainment by him of age 65, but in such case the retirement allowance shall not exceed one-third of his final compensation.(Amended by Stats. 1961, Ch. 1695.)