Section 55. Any town may authorize the selectmen to appoint a town accountant, who shall perform the duties and possess the powers of town auditors as defined in sections fifty to fifty-three, inclusive. In towns so authorizing the appointment of a town accountant the office of town auditor may, if the town so vote, be abolished. In towns which have accepted chapter thirty-one or corresponding provisions of earlier laws, the appointment of the town accountant shall be subject to the civil service rules. The town accountant shall be sworn to the faithful performance of his duties, shall hold no other town office involving the receipt or disbursement of money, shall hold office for three years and until a successor is qualified; provided, however, that at the discretion of the appointing authority, a person may be appointed to the position of town accountant for a term of not more than five years and until a successor is qualified. The town clerk, if he holds no other office involving the receipt or disbursement of money, may be appointed to the position of town accountant.