Any municipality in this State which does not operate under the commission form of government and which had a population of (a) not more than sixty-five thousand and not less than ten thousand, (b) not more than seven thousand and not less than six thousand five hundred or (c) not more than six thousand and not less than five thousand five hundred, according to the United States census of 1970, may by ordinance provide for a civil service commission for such municipality, to be administered by not more than five commissioners to be elected by the city council of such municipality, with the duties, powers and authority conferred and authorized by this article. One member of the first commission so created under this article shall be chosen for one year, one for two years and the other for three years. Thereafter at the expiration of each respective term of office the city council shall elect a commissioner for the term of three years so that the term of office of one member shall expire each year. Vacancies shall be filled by the city council for the unexpired term.

If a municipality chooses to have five commissioners, of those initially elected one shall be elected for one year, one for two years, one for three years, one for four years and one for five years. Their successors shall be elected to serve for terms of five years and until their successors are elected and qualify.