The T 1 was one of the locomotives that were developed and built directly for the Oldenburg State Railways. These were four-coupled engines with an axle load of less than ten tonnes, which were planned for shunting services and construction trains.
For the first series, built between 1871 and 1873, support was obtained from Krauss in Munich. The result was a modern design that was powerful despite its small size. However, the production took place in the company's own workshops and comprised twelve engines. These were given partly bizarre names, such as “Schnipp”, “Schnapp”, “Schnurr”, “Tick”, “Tack” and “Tuck”, what describes some noises in German. A wheel diameter of just 1,020 mm only allowed a speed of 40 km/h and a high tractive effort. With a boiler pressure of ten bars, they were up to date, but an unladen weight of only 11.3 tonnes could still be achieved. At less than 6.50 m, the class was one of the shortest standard-gauge locomotives ever built in Germany.
Another series of 18 upgraded engines was purchased between 1888 and 1892 and designated T 12. This time the production was taken over by Hohenzollern in Düsseldorf, who had more experience and a larger capacity than their own production facilities. These were significantly heavier than the T 1 and had a boiler pressure of twelve bars, which was common for modern designs at the time. With a driving wheel diameter of now 1,130 mm, the maximum speed could be increased by five km/h. In addition to the higher boiler pressure, the cylinder diameter was also increased by five millimeters.
In the period that followed, they faced competition from the T 2, which had been developed on the model of the Prussian T 2 and, above all, made the original T 1 superfluous. Five more of the newer type came to the Reichsbahn as class 9874. They received the numbers from 98 7401 to 98 7405 and were retired in 1931.