Any member of a police department who has resigned therefrom or who shall resign therefrom, or who has been granted or shall be granted a leave of absence to serve in the armed forces of the United States or armed forces reserve thereof, or who shall have been selected for training under the selective service provisions of the laws of the United States and has returned with an honorable discharge from, or other document showing honorable service in, such service to the police department, shall have the period of such service included as part of the person‘s period of service in the department.