Notwithstanding the provisions of Kan. Stat. Ann. §§ 74-4913 to the contrary, any employee of a participating employer who became a member of the Kansas public employees retirement system on September 1, 1962, who was previously employed by said participating employer on March 1, 1938 until June 30, 1941, shall upon retirement be granted 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 one hundred forty dollars ($1,140.00).