239. English Balance Scale. Roberval principle. Equal arm. Oblong, white porcelain base 6-7/8" wide x 4" deep, bow-shaped leading edge. Four porcelain legs. Three nested brass weights in recess in base. Brass pillar and plates. One plate embossed with phrase, "New Rates of Postage" and rates in oz. and pence for "Letters" and "Book Post."