Maker's badge reads The Medical Supply Association, 167-175 Gray's Inn Road, London. Circa 1915 according to the Science Museum.
Accurate weighing for persons up to 24 stone. To weigh yourself you add the circular cast iron weights (marked in stones, but smallest is marked 7 lb ie half a stone) to the 'hanger' (on the right in the photos) until the balance bar is nearly level. Then you fine tune by sliding the movable weight along the bar until it is dead level - then read off the pounds on the scale which has divisions 1 to 7, and ounces as each pound is subdivided into 8 giving accuracy to 2 oz (ounces)!
Hope that makes sense, it's very easy in practice and also much more fun than digital scales - and very cheap to run with no batteries to replace! No maintenance as very sturdy and simple construction.
In the final photo the amount of weights added to the hanger, together with the position of the sliding weight, signify a person's weight of 15 stone 5 lb 8 oz (but as there is no-one standing on the scales the balance bar is not level)
Base 24"deep x 11"wide; Arm 20"wide; height 36". Weight of scales itself is not known, but heavy.
Collection in person only, but buyer can organise their own courier to collect.