Notwithstanding the provisions of Kan. Stat. Ann. §§ 74-4913 to the contrary, an employee of a participating employer having been reemployed on December 1, 1962, and becoming a member of the Kansas public employees retirement system on December 1, 1963, who was previously employed by said participating employer from May 1, 1939, to September 30, 1941, shall upon retirement be entitled to prior service credit for all service with said employer prior to January 1, 1962. The prior service benefit shall be computed by using a prior service annual salary of one thousand two hundred dollars ($1,200).