Print depicting John Harrison (1693-1776), seated next to a table showing his famous marine timekeeper, H4. The text on the print describes it as an engraving by William Holl from an engraving by Pilippe Joseph Tassaert published in 1768, after a painting by Thomas King (ZBA 2249). This print was published by Charles Knight (1791–1873) at Ludgate Street in London under the superintendence of the Society for the Diffusion of Useful Knowledge, originally in 1835. See prime copy, PAD2851.

The SDUK, which aimed to distribute suitable and cheap literature to the working classes, was founded by Lord Brougham in 1826. It was chiefly active in the 1830s and was wound up in 1848. Charles Knight was their chief publisher.