561. English Balance Scale. Roberval principle. Equal arm. All brass. 3-3/8" high; oblong base 8" wide x 4" deep. Round plate for weights; oblong plate for letters, inscribed "Rates of Postage" in oz. (1-8) and pence (1-3). Three brass receptacles on base hold matched weights (1, 2, 4 oz.). Signed: "Mordan & Co. London."