56.—Where as regards any fishery year a regional board strike a rate under section 55 or the Minister, by reason of the failure of the board to strike the rate, strikes a rate under that section for the fisheries region of the board, the board or the Minister shall make the rate according to the valuations appearing in the revised Valuation List required under the Valuation Acts to be issued by the Commissioner of Valuation by the 1st day of December immediately preceding the commencement of that fishery year, and the board may levy, collect and recover any sum due on account of any rate so made, notwithstanding any pending appeal or notice of appeal under the Valuation Acts with respect to valuation but where the valuation of any fishery is altered on appeal, the board—

(a) shall, if the valuation is decreased, repay any sum paid in respect of the rate in excess of the sum which would have been payable if the valuation had originally stood as altered on appeal, and

(b) may, if the valuation is increased, recover as arrears of the rate, an amount equal to the difference between the sum payable in respect of the rate as made and the sum which would have been payable in respect of the rate if the valuation had originally stood as altered on appeal.]