Limited space between the frames required them to have outside cylinders and Walschaerts valve gear unlike their 5 ft 3 in (1,600 mm) broad gauge counterparts.

Two engines were ordered from Beyer, Peacock & Company in January 1892 and left Manchester in May 1892 entering service as numbers 69 and 70.

The class would only be enlarged after the BNCR had amalgamated with the Midland Railway to become the Northern Counties Committee (NCC).

The next engines were built by the NCC at York Road works to transport valuable iron ore traffic, that had been obtained in 1907, from the mines at Parkmore to Larne Harbour via Ballymena.

When starting a locomotive from rest, a simpling valve was opened which admitted steam directly from the boiler to the low-pressure cylinder as well as the high-pressure one.

Not only did this provide maximum tractive effort when starting but also avoided problems that might arise if the high-pressure piston was in a dead centre position.

The initials "NCC" were sited on the side tanks, in shaded serif gold capitals, placed in front of the number plates.

Under the Ulster Transport Authority, the narrow-gauge engines, for which there was no long-term future, continued in the unrelieved black wartime colour scheme.

This was eventually enlivened on Nos.43 and 44 by vermilion and yellow lining: The UTA roundel, 14in in diameter, with "Ulster Transport" in orange block capitals, lined in red, surrounding a white shield bearing the red hand of Ulster, all on a mid-green background, was placed in the middle of the side tanks of Nos.