Okla. Stat. tit. 19, § 951

The board of county commissioners of any county in the State of Oklahoma having a population of more than three hundred thousand (300,000), according to the latest Federal Decennial Census, is hereby authorized to provide by resolution for a retirement fund and system for any or all of the employees of such county as delayed compensation in order to encourage continuity of dedicated service on the part of employees and thereby promote public efficiency, and to provide retirement allowances and other benefits for such employees, their surviving spouses and surviving children; such fund to be supported by joint contributions by such county and the employees to be benefited.