Whenever a position upon the Police Department of the City is to be filled, with the exception of the position of Chief of Police, the Chief of Police shall notify the Commission of that fact, and the Commission shall then certify to the Chief of Police the name and address of two or more candidates in the discretion of the Commission, but not exceeding three, standing highest upon the register for the class or grade to which the position belongs. The Commission shall not certify the name of any person who, in the judgment of the Commission is not of good moral character or who has secured a place upon the eligible list by fraud, concealment of facts, or by violation of the rules of the Commission; and having certified such person, they shall cancel said certification and remove the name of any such person from the eligible list.