Also in 1876, the Caledonian Railway bought from Neilsons four locomotives of the same design.
Between 1885 and 1908, the Caledonian built thirty-four more, at the company's own works at Glasgow St Rollox.
North British Railway
The "G" class on the North British Railway came about in much the same way – the NBR bought two locomotives from Neilson in 1882, and by 1899 they had built thirty-six for themselves at their Cowlairs Works.
Effectively, Neilsons seem to have licensed the design to the two main line railways, both of whom built it with detail modifications and then ascribed the design to their Chief Mechanical Engineers, Dugald Drummond and......