Interesting variation of Fairbank´s standard letter steelyard mounted on a cast iron base. Patented 2 May 1878 No. 1774 A.M. Clark 

"A half-roberval and steelyard letter scale has a beam which can be rotated about its longitudinal axis. When turned in one direction, graduation in ounces are displayed, when turned in the other direction, graduation in grams can be used."