(2) The board shall prepare and keep a register for each grade or class of positions of the persons eligible for promotion. Such register shall contain information concerning merit in service, fidelity in service and seniority in service. Such persons shall take rank upon the register as candidates for promotion in order of their relative excellence, as determined by merit in service, fidelity in service and seniority in service. Candidates of equal standing shall take rank upon the register according to the order in which their applications are filed. [Amended by 1969 c.262 §6]