This is a large brass barrel mounted 'Cooke Process Lens' engraved for 'Taylor, Taylor and Hobson' and marked 18 inch focal length. It is additionally engraved 'Cooke Process Lens' and retailed by' A.W. Penrose and Co. Ltd', linking it directly to the professional photographic trade. The construction is substantial, with stepped brass bands and large threaded mounts designed for fitting to a process or large plate camera.

Internally the iris diaphragm is visible and the multi blade aperture mechanism can be seen through the glass. The front and rear elements sit within a heavy brass housing typical of pre-war optical manufacture. The scale and focal length indicate intended use on large format equipment where precision and flat field reproduction were essential.

An 18 inch Cooke Process lens was not a casual amateur item but professional equipment used for reproduction work, printing blocks and large plate photography. It reflects a period when British optical engineering was competing internationally and supplying the growing commercial photographic industry.