The North British Locomotive Company of Glasgow built 30 or so of these small 0-6-0 tank locos, over a five year period from 1898 to 1902. They passed into LNER ownership in 1923, and then into BR hands in 1948. All were withdrawn by 1962. I have built one of these locos by modifying the Dapol/Hornby 00 gauge 'Terrier' tank loco.
Start by removing the unwanted details, i.e. the boiler top piping and the pipes leading from the pressure dome. Then remove the cab roof. Carefully slice off the buffers and reattach to the buffer beam proper at 20mm spacing.
The chimney is next. Slice off the chimney cap and then shorten the chimney by 4mm. Glue the chimney cap back on to the remaining part of the chimney.
Make a start on the roof by filing the straight edge of the 'Terrier' roof to a gently rounded profile. Mark off the corner of the cab front and rear 2mm down from the top before filing down.
Extend the bunker by using the parts supplied in the box. Cut the bunker 2 ribs down from the dummy coal load.
If a J83 is required, then this can be made by removing the box from the rear of the bunker and bringing the rear buffer beam back so that is flush with the cab rear. Also, add the pressure valves from the parts supplied with the 'Terrier'.
Livery is left to individual choice - though my J82 is BR black.
Well, there you are. A nice wee loco which looks the business and runs superbly. All I need now are some 1:87 scale BR Mk1 suburbans or, maybe, some LNER tourist stock.