A contract is authorized between the city and the board of administration, California public employees' retirement system, a copy of which, as amended, shall be on file in the office of the city clerk and is made a part of this article as though set forth herein in full. Such contract shall provide for the participation of the city in the public employees' retirement system and shall make city employees members of such system with all rights and benefits conferred by the public employees' retirement law, including benefits for prior service. (1962 Code § 2-6.301)