Model Boulton & Watt bell crank engine, c. 1799. The bell-crank engine design was devised for Boulton & Watt by William Murdock, one of their employees. It was the first 'independent' (self-supporting) engine to be built.
It is often possible to identify the maker of a model from its workmanship. Details of this model are similar to those on others built by William Murdoch, who was responsible for the conception of the bellcrank engine, the first small and self-contained steam engine available.