Class 01.10 was a further development of the 01. A total of five series or batches were delivered, each with minor variations: 01 001–010 (1926), 01 112–076 (1927–28), 01 077–101 (1930–31), 01 102–190 (1934–1936), 01 191–232 (1937–1938). Even in the 1930s the employment of Class 01s was limited to the relatively few routes that had already been modified to take a 20-ton axle load. From Berlin outwards they were the Anhalt, Lehrte and Hamburg lines. The Berlin City Railway had first to be strengthened by reinforcing the viaduct arches. Up to 1930, the first 90 engines were stationed at the locomotive depots of Essen, Nuremberg, Erfurt P, Berlin Ahb, Hamm, Magdeburg Hbf, Kassel, Hanover, Hamburg Altona, Bebra and Offenburg. From 1931 they were also stabled at Frankfurt (M) 1, Berlin Leb, Braunschweig, Berlin Pog, Schneidemühl, Königsberg, Göttingen P, Paderborn, Dresden Alt, Breslau, Cologne Deutzerfeld, Hof and Halle P. Originally, the Class 01's top speed was restricted to 120 km/h. In order to raise this to 130 km/h, the diameter of the leading wheels was changed from its original 850 mm to 1,000 mm on locomotives from operating number 01 102 onwards and brake effort was increased by installing double-sided working of the brake shoes on the coupled wheels and by braking the trailing wheels. The air and feed pumps were located in smokebox recesses behind the large Wagner smoke deflectors, which had been fitted from 01 077 onwards. (Earlier models were also refitted with Wagner type deflectors later). This made access to the pumps for maintenance purposes more difficult and later Einheitsloks had their pumps located in the middle of the vehicle on delivery. The Deutsche Bundesbahn converted their engines to the smaller Witte smoke deflectors and moved the pumps to the running board in the centre of the vehicle. The Deutsche Reichsbahn in East Germany shied away from such major changes to the load distribution, so that only minor modifications in appearance can be seen even in their last years. From the third series (01 077 et seq.) the boilers were delivered with longer smoke tubes and thus a shorter firebox. All engines originally had a central lock for the smokebox door. The first locomotives had gas lighting on delivery; from 01 010 they had electrical lighting and the last few batches were given a third headlight. The Class 01s were equipped with 2'2 T 30, 2'2' T 32