Notwithstanding the provisions of Kan. Stat. Ann. §§ 74-4913 to the contrary, a county engineer of any county who first became a member of the Kansas public employees retirement system on February 1, 1963, while in the service of a participating employer with which he had served over twenty-five (25) years prior to becoming a member shall receive prior service credit for employment with a participating employer for any employment performed before January 1, 1962, whether such employment was continuous or not. The prior service annual salary in such case shall be the highest annual salary (not including any amounts received as payment for overtime or as reimbursement for traveling or moving expense) received for personal services by the member from the current employer in any one of the three (3) calendar years immediately preceding January 1, 1962.