In the event that it both happens (1) that a municipality or other appointing authority shall hereafter become subject to this section and (2) that at the time such municipality or other appointing authority becomes subject to this section it then has in its employ employees or appointees who would come within the classified service as defined in this section, the board in its discretion may extend or grant permanent status to any or all such employees or appointees. The board in its discretion may extend or grant permanent status to any or all employees or appointees employed or appointed by the county board of health or the board of registrars, municipality, or other appointing authority at the time this section becomes effective including appointees of employees who are absent by reason of military service of the United States. The personnel board shall also have the authority to take into account in determining the rights, privileges, benefits, and liabilities of employees or appointees of the appointing authorities the previous records of such employees and appointees in their employment by the respective employer. Whenever the appointment or employment of new or additional officers or employees of such counties, municipalities, or appointing authorities, therein, is hereafter authorized by law, such officers or employees shall be subject to the provisions hereof and included within the county and municipal civil service unless of a class excepted herein.