The South African Railways Class 1B 4-8-2 of 1904 is a steam locomotive from the pre-Union era in the Natal Colony.In 1904 the Natal Government Railways placed fifty Class B locomotives with a 4-8-0 Mastodon wheel arrangement in service. Of these, six were modified in 1906 to Altered Class B locomotives, the first in the world with a 4-8-2 Mountain wheel arrangement. In 1912, when those six were assimilated into the South African Railways, they were renumbered and classified as Class 1B.