In 1821, Sir William Congreve patented a process he described as compound-plate printing, with the aim of countering rising levels of banknote forgery. Two of the machines used in the printing process, a geometric lathe commissioned by Congreve from the London engineer Bryan Donkin and a later pantograph engraving machine, have recently been acquired by the Science Museum . This paper looks at the introduction of compound-plate printing and its associated technologies within the context of the wider battle against forgery. It consists of four parts. The first considers the restriction period from 1797 to 1821, when the exchange of paper credit for gold was suspended. The second looks at the characters involved – Congreve, Donkin and their American competition. The third section is a study of the machines themselves, and the final section looks at how Congreve’s process was adopted in the wider world.
The geometric lathe and the pantograph engraving machine stand at a timely intersection of economic imperative with technical achievability. It seems highly appropriate that machines embodying new levels of precision and ingenuity should have been proposed to underpin confidence in the paper credit upon which Britain’s expanding machine economy relied. However, a study of the machines suggests that the process by which they were designed and built was by no means straightforward.