Model of an independent type 'Cabinet' rotative beam engine, with self-supporting iron frame and cistern bed, made by Boulton, Watt & Co., and owned by James Watt, c1813, with tin container, for cigarettes, containing nineteen steel flat washers, fourteen slotted brass dome-head machine screws and an ‘L’ shaped flat piece of wood.

From 1799 until 1813, Boulton, Watt & Co. pioneered small, self-contained steam engine manufacture in the form of the bellcrank engine, referred to them as the small side-lever engine. This was to meet the growing demand for small and self-contained engines. However, from 1813 the bellcrank engine was superceded by this more conventional design, with the beam above the cistern bed containing the condenser. Only the outboard crankshaft bearing needed to be independently mounted, resulting in a graceful yet compact design. This model was owned by James Watt.