William Ladd (Margate, Kent 1815 – London 1881) was a renowned maker of scientific instruments between 1842 and his death. He is best remembered for the chain-driven focusing mechanisms of his microscopes. Microscope slides are occasionally found as Ladd sold them at retail. Ladd was also known for his pneumatic apparatus and his innovative forays into electricity. Although he did not number most of his instruments, his business occupied five different locations, which help to date them. The main ones were at No. 3 Cleaver Street, Kennington, Lambeth, Surrey, where it was located from early 1841, and from 1860, at 11-12 Beak Street, near Regent Street, London.

This microscope follows the structure of the “Jackson” model, which is characterized by offering a rigid optical plane, based on a continuous bar, that supports the body of the instrument on the stage and carries a small secondary body underneath. This model prevailed over the previous ones and has lasted until today. It is engraved with the address where he worked since 1860 and, having a chain transmission, it probably dates from the early 1960s. Focusing is not done by a rack mechanism, but by a chain that is wound around a spindle that rotates by means of two adjustment screws, which provides a remarkably smooth movement without play that allows fine adjustment to be eliminated.