From J.E. Minns, Model Railway Engines (London: Weidenfeld and Nicolson, 1969). The author writes:
"Timothy Hackworth's little-known 4-1/2 gauge model 0-4-0 locomotive. It is the original design of the Sans Pareil of 1826. Here one can see how closely Hackworth and Stephenson worked. The vertical semi-immersed cylinders and valve arrangement are typical of Stephenson's Killingworth engines, whilst the method of connecting is reminiscent of Hedley's model. It is hot-coals-fired. 13-1/2 ins by 9-1/2 ins long."