Scale: Unknown. A demonstration model of double cylinder steam engines, as to be used on board HMS 'Rifleman' and HMS 'Sharpshooter' (both 1846), gunboats. The majority of the model has been cast and turned in brass and gilded, in particular the supporting framework, large and smaller toothed flywheels, crankshaft and connecting rods. There are four cylinders, two large and two small, which have been turned in wood and painted black. The whole model is screwed to a square, stained mahogany baseboard on which is glued a paper handwritten label inscribed "Model of a pair of double cylinder engines designed for working a screw propeller... HMS "Rifleman & Sharpshooter" by Wm Fairbairn & Sons". Number "7" on base. The model can be worked either by turning the large flywheel or the crankshaft to show the operatiing sequence of the cylinders and crankshaft.