A form of balance in which the body to be weighed is suspended from the shorter arm of a lever, which turns on a fulcrum, and a counterpoise is caused to slide upon the longer arm to produce equilibrium, its place upon this arm (which is notched or graduated) indicating the weight; a Roman balance; -- very commonly used also in the plural form, steelyards.

a portable balance consisting of a pivoted bar with arms of unequal length

a weighing instrument that uses balances and counterweights.

The Steelyard, from the German Stalhof, was in the Middle Ages the main trading base of the Hanseatic League in London.