This unique orrery was designed to focus specifically on the planet Saturn, its rings and system of satellites. An engraved inscription shows that it was designed and made by William Lacy in 1779. The orrery is supported on a circular, wooden base, mounted on three legs. On the top is an engraved brass plate with calendar and zodiac scales.

The planets Earth (with moon), Jupiter (with four satellites) and Saturn (with five original satellites, one of which is missing, and two later additional satelites, one of which is missing) are ivory, supported by brass arms and manually-driven gearing, although this is now jammed. It is likely that there was once a central attachment representing the Sun, Mercury and Venus. There is another sphere placed on top of the model of the Earth, although it is unclear what this represents, the model of the moon is supported by a brass disc, while another brass disc beneath is placed at an angle, perhaps representing the ecliptic plane. Five of Saturn's satellities are attached to gears so that they can rotate around the planet. These would appear to be the five of Saturn's moons known in 1779, Tethys, Dione, Rhea, Titan (missing) and Iapetus. Another flat brass plate is attached to the arm but not to the gearing mechanism, supporting another two satellites (Mimas and Enceladus, one of which has been lost, although the arm survives and is numbered AST1066.1). These were discovered by William Herschel in 1789, and this plate would appear to be a later addition dating from around this time.

The maker, William Lacy, is mentioned by Nicholas Goodson in ;'English Barometers 1680 - 1860', as a barometer maker and apprentice to Francis Van der Meulen. His address is given as West Street, West Smithfield. He was also author of 'An Introduction to Astronomy' (1777). This book included advertisements for some of his philosophical instruments, sold from his house at 145 Drury Lane, including "Lunariums" that showed "all the phenomena of Saturn's ring and five moons, as seen from the earth and sun, in every year". He also made similar models that focused on Jupiter and its satellites.