The NSB type 25 was a 0-6-0T tank locomotive used for shunting and transfer duties. Compared to the type 23, it had a lower axle load. Its basis was the type F of the NHJ (Norsk Hoved-Jernbane). There were five variants which were designated 25a to 25e and weighed between 33.2 and 36.2 tonnes. Only the 25d had a superheater, all others were saturated.
Of a total of 37 locomotives from the initial production period between 1909 and 1922, the highest number came from Hamar Jernstøberi with 19. Baldwin from Pennsylvania delivered nine, Thunes Mekaniske Verksted three and Norsk Maskin Industri six. In 1947, the Swiss SLM delivered five more which were similar to the E 3/3. They were retired between 1958 and 1970.