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 September 1, 1969, who received prior service credit at that time, who retired under the Kansas public employees retirement system on August 1, 1970, who was first employed by another participating employer from October, 1941, through December, 1945, who was again employed by another participating employer on January 1, 1946, through August 31, 1954, and who was again employed by another participating employer on November 1, 1964, through August 30, 1968, shall upon the effective date of this act receive additional prior service credit for all such service with participating employers as described in this section. The prior service benefit shall be computed by using a prior service annual salary of twelve thousand dollars ($12,000).