Ladder scale made by DeGrave & Co, London. The lower beams are set for fixed weights of 1, 2 and 3 oz, respectively. Each of this three beams has a turn-over weight to convert from oz to 20, 40 and 60 grams. The top beam is pre-weighted for 4 oz, and further weights can be added as required. Brass on a mahogany base. 12" tall. Examples made for the Post Office are marked GPO.