Sheffield (formerly Sixteen) is based on a Hunslet Austerity WD 0-6-0ST. Other members of this class were featured in Thomas and the U.K. Trip and the Down at the Station segments. Sheffield's livery bears a striking resemblance to a member of this class, 3823 "Warrior" which worked at the National Coal Board. It is possible that Sheffield could be based on the Wemyss Private Railway's No. 16. The engine has the basis, wears a similar livery to him and while there is no record of a steelworks on the railway, the engine had replaced an engine (ironically carrying the same number) that had an accident similar to Sheffield's.
