The Hokkaidō Colliery and Railway Company, and thus all the Class 7100 locomotives, came under the control of the government in 1906, with the passage of the Railway Nationalization Act, which incorporated it into the Japanese Government Railways. The numbering of train series was standardized and formalized in 1909, officially establishing these eight locomotives as the Class 7100 (7100-7107). The engines' names were dropped, and some changes were made to the vehicles, in particular the one purchased by the government in 1899, which was made to have two separate repeat-transferring boilers. Three vehicles were left entirely unaltered. At this point, No. 7103 was traded away, while the other seven entered service under the Hokkaidō governmental construction bureau.