Fifty three similar locomotives were built by the North British Locomotive Company between June 1910 March 1917 with longer cabs but shorter bunkers. They were fitted with Steam brakes and used on Freight duties. A further batch of ten locomotives was built by North British Locomotive Company in February and March 1920. A third batch of ten was on order from Robert Stephenson and Company when the North British Railway became a constituent of the LNER. They were delivered between January and March 1923. They weighed 60 LT (60.962814527999 t) and were numbered to fill gaps in the sequence between 20 and 926. Two of these locomotives were later fitted with Westinghouse brakes in 1929 and were re-classified N15/2. The remainder were withdrawn between 1957 and 1962. .
Six N15/1 locomotives were built by the North British Locomotive Company with Westinghouse brakes in 1910 nkers. They were used to bank passenger trains up the 1 in 42 Cowlairs incline leading from Glasgow Queen Street railway station. Prior to 1910 trains had been roped hauled by a stationary engine. A further two N15/1 were converted to N15/2 in 1929. They weighed 62 LT (63.0 t) and were numbered to fill gaps in the sequence between 7 and 282 and were withdrawn between 1957 and 1962. .