These engines were followed by another eight in August 1913, numbered in the range from 1502 to 1509, and ten more in January 1915, numbered in the range from 1510 to 1519, all built by NBL.
In June 1921, Beyer, Peacock and Company (BP) delivered the final twenty Class 12 locomotives, built in two batches of ten and numbered in the range from 1859 to 1878 [REF].