The NSB (Norwegian State Railways) Class IV (as in the number four, or "fire" in Norwegian) or Tryggve Class was a class of 1,067 mm (3 ft 6 in) narrow gauge 2-4-0T steam locomotives built by Beyer, Peacock & Company in Manchester, England. The 3 ft (914 mm) gauge Beyer Peacock locomotives built for the Isle of Man Railway strongly resemble this design.
Further reading
Bjerke, Thor; Hansen, Trond B.; Johansson, Erik W.; Sando, Svein E. (1987). Damplokomotiver i Norge. Norsk Jernbaneklubb. s. 222–224, 232–233. ISBN 82-90286-09-0.