They operated services throughout the NCC's 5 ft 3 in (1,600 mm) broad gauge system in the north-east of Ireland.
These had been built by Beyer, Peacock & Company in the 1890s to the design of the BNCR Locomotive Engineer Bowman Malcolm.
During rebuilding, they were fitted with LMS standard boilers that had to be placed higher than the originals to allow the firebox and ash pan to clear the rear driving wheel axle.
The closely coupled driving wheels accentuated the appearance of the high-pitched boiler, earning these engines the nickname of "Whippet" because of a perceived resemblance to the breed of racing dog.
The initials "NCC" in shaded serif gold capital letters were placed centrally on the tender sides.
Number plates were brass with raised digits and edge; they were carried on the lower cab sides with another placed centrally on the back of the tender tank.