I cant be positive which class of loco the builder chose to construct here, but my best guess is a GWR 1076 Class. In truth there were several classes of outside frame pannier tanks and some of these were rebuilt from tender engines so theres lots of choice here. The 1076 Class were also known as Buffalos and were built in different forms including pannier tanks and saddle tanks. There are plenty of pictures and drawings available of the different variations in the fantastic 'A Pictorial Record of Great Western Engines' by J H Russell (volume one).
The chassis is very nicely made and I'm sure it will make the base for a super model. The boiler is made to LBSC's Pansy design and was built by the well known boiler maker Alec Farmer in 1977. Alec wrote a least one book on the subject of boilermaking and Engineering in Miniature are currently re-running a series of articles by him on the subject.
