Bank of England Bullion Balance of 1820. Steel beam 28" long inscribed on one face "Bank of England AD 1820" and on reverse face "J. Barton, Invr. AD 1820; Maudslay and Co. Fecerunt". Fitted steel knife edges, pan shackles with double steel bearing planes, downward pointer and gravity screw bobs for sensitivity adjustment

Equal-arm scales by Maudslay & Co., London, made for the Bank of England in 1820 weighing gold and silver bullion. Designed by J. Barton the balance is fitted with steel knife-edges and a release mechanism for locking the beam. Equal-arm balances of this type are the simplest and earliest method of weighing. They consist of a beam that has a pan suspended at either end. In use objects to be weighed are placed in one pan while weights of known mass are placed in the other pan until the two are balanced with the bar level. The product of these weights gives the mass of the commodity being measured.