Notwithstanding the provisions of Kan. Stat. Ann. §§ 74-4913 to the contrary, a county probate judge who elected to become a member of the Kansas public employees retirement system effective March 1, 1968, and the county entry date was January 1, 1968, and who was employed by another participating employer on May 4, 1942, through March 31, 1951, shall upon retirement be granted service credit for all service with all participating employers prior to January 1, 1968. The prior service benefit shall be computed by using a prior service annual salary of five thousand two hundred dollars ($5,200).