Notwithstanding the provisions of Kan. Stat. Ann. §§ 74-4913 to the contrary, an employee who became a member of the Kansas public employees retirement system on April 1, 1962, who was first employed by another participating employer periodically from September 1, 1927, until May 31, 1936, shall upon retirement be granted prior service credit for said employment. The prior service benefit shall be computed by using a prior service annual salary of two thousand six hundred forty dollars ($2,640).