Fifty of these vehicles were built between 1889 and 1891. All were withdrawn between 1929 and 1938 except for one fitted with a loading gauge frame in 1933 for tunnel inspection. It was eventually withdrawn in 1961.
The N6 body design was based on the N5 horse box of which only one was built. The most obvious difference between the two diagrams was the tumblehome sides and ends of N5 in comparison to the plain flat sides of N6. The basic underframes were similar, though N5 had the earlier outside rigged brake gear, superseded on N6 by the later standard pattern with triangular tie-bars between the brake blocks.
These vehicles were seen throughout the GWR area and on occasions nationwide.