Brookes’ Portfolio Manufactory, located in Coventry Street, London was a business run by Henry Brookes and his partner Abraham Jones. The artists used a ‘mathematical instrument’ to draw silhouette portraits in a cheap and efficient manner. Machine-produced silhouettes were popular at the time, but Brookes and Jones were keen to emphasise the unique exactness of their ‘mathematical’ machine, of which no detailed descriptions have survived. An advertisement states, “if they [silhouettes] are not put together with mathematical exactness they can never work true”.
Source: McKechnie (Author of, British Silhouette Artists and their Work 1760-1860)
Brookes' Portfolio Manufactory (McKechnie Section 3)