Notwithstanding the provisions of Kan. Stat. Ann. §§ 74-4913 to the contrary, an employee of a participating employer who became a member of the Kansas public employees retirement system on May 1, 1964, who was first employed by another participating employer on January 1, 1955, and worked continuously with said other participating employer until December 31, 1962, shall upon retirement be granted prior service credit for all service with said other participating employer. The prior service benefit shall be computed by using a prior service annual salary of three thousand six hundred twelve dollars ($3,612).