Thomas Mudge's pioneering work in the 1750s and 1760s created a new type of escapement for portable timekeepers - the lever escapement. Mudge's original concept had been a complicated one which was difficult to replicate, even by the best watchmakers, and it was not until the 1780s that the lever escapement was developed by Josiah Emery of Charing Cross, London. Emery employed a highly skilled escapement maker, Richard Pendleton, and the result of their combined efforts was a series of pocket watches with Emery's lever escapement design.This particular example is signed 'Josiah Emery, Charing Cross, London 1089' on the movement. The 18 carat gold case is hallmarked 'London 1786' and bears the mark 'VW', Valentine Walker, who was a watch case maker of Clerkenwell, London.The white enamel dial is of the so-called 'regulator' type. The minutes are marked around the outside and, above the centre, separate subsidiary dials for hours, with seconds below. The movement is characteristic of Josiah Emery's work, with finely gilded plates and a decoratively engraved bridge on the back plate for the balance. The gear train consists of the standard four wheels which drive the lever escapement. This, in turn, is controlled by a temperature compensated balance, known as the 'double S', designed to obviate timekeeping errors caused by temperature change.