Miller's Vacuum Balance [comparator], by L. Oertling, 1870, glass side caps (broken glass replaced 18/ 10/33). Length of beam 1'-4", sensitivity 0.0042gr.

William Allen Miller (1817-1870) designed this balance. Built by L. Oertling, London in 1870, it was used for comparing primary and secondary weights at the Standards Department at Westminister. The balance is fitted inside a sealed chamber so that the weighing can be carried out in a good vacuum. It is fitted with a system of rods and levers to allow the weights to be moved to and from the scale pans of the balance.