In order to do something about the inefficient use of old steam locomotives in shunting service, the I e was designed for the Württemberg State Railway as a four-coupled tank locomotive. During development, however, attention was also paid to the fact that the engines could be used in line service on branch lines if required. They were designed as a cost-effective and purposeful construction. By using the 20 mm thick plate frame as a water tank, the coal bunker could be moved in front of the driver's cab, which reduced the overall length of the locomotive.

On the boiler barrel, the steam dome and the regulator were separate from each other, with a sandbox between them. The Allan valve gear had to be on the outside and the drive was on the second axle. With a driving wheel diameter of 1,235 mm, speeds of up to 60 km/h could be reached. In addition to a modern air brake, some of the machines also had a countersteam brake.

30 were delivered in several batches, of which 25 units were taken over by the Reichsbahn in 1925. Together with the I b taken over from the Pfalzbahn, they were classified in the class 88⁷⁵. By 1930 all were retired or sold to private operators. One example was on Austrian territory after the end of the Second World War after it had been used by a construction company. It was taken over by the ÖBB and used until 1956, making it the last representative of the I e.

When the Crampton locomotives used for express trains on the Grand Duchy of Baden State Railways were no longer state of the art, a new express locomotive was developed from the class III passenger locomotives.

Special features of the II a were the Belpaire firebox and an outer plate frame. The power was transmitted via Hall cranks to the drivers located within the frame. Because the cylinders were located in front of the pivot of the lead bogie, the running smoothness was not entirely convincing. Especially under full load, the overhanging masses of the cylinders generated unwanted vibrations.

Despite this, the locomotive performed well and was used on the international trains that traversed the Baden region. The locomotives were able to pull a 220-tonne train with 16 cars on the flat at up to 84 km/h and thus still reached 60 km/h on a gradient of 0.5 percent. At 1.25 percent, 150 tonnes could still be pulled at 50 km/h.

Another delivery of ten locomotives in 1891 saw the need to lengthen the boiler tubes and increase the diameter of the cylinders to 457 mm. To improve the running characteristics, the wheel base of the bogie was also increased from 1,400 to 2,000 mm.

After the founding of the Reichsbahn, the II a met the same fate as other older Länderbahn locomotives. Of the 24 units built, ten were still included in the renumbering plan as class 36⁷³. Eventually all were retired by 1925.

The class II c designated express locomotives which, contrary to usual practice, had been developed based on the English practice. They were the first locomotives in Germany to be certified for a maximum operational speed of 110 km/h. The clearest distinguishing feature was the inside plate frame with wheel housings, which partially covered the 2,100 mm large coupled wheels and started at the level of the very low running board. In addition, the cylinders were on the inside, which was very rare in Germany for two-cylinder steam locomotives.

Due to the long wheelbase of the bogie and the low-lying boiler, the running characteristics were very good, so that the locomotives even ran smoothly at 120 km/h during test drives. The large wheels also helped maintain higher speeds for longer periods, and thus the 110 km/h certification was granted.

The development and production of the first series models took place at Grafenstaden in Alsace, but further vehicles followed from the Karlsruhe Engineering Society and the Saxon Machine Factory Hartmann. A total of 35 pieces were made between 1892 and 1900.

In order to reduce the effort required at high speeds, two modifications were made to the last five machines, as would also be found on later locomotives. One was a wind-cutter cab, i.e. the front wall of the cab was divided vertically in two and both halves were pulled back at a sharp angle in a V-shape. The other adjustment was an aerodynamically clad smokebox door. Instead of being conical like other German express locomotives from the beginning of the century, the tip was pulled down almost to the bottom of the boiler and the fairing formed a transition to the cylinders. Along with these modifications came an increase in boiler pressure from 12 to 13 bar.

Despite their good running characteristics, the tractive power of the locomotives was soon no longer sufficient for lighter express trains, as these could pull a maximum of 260 tons at top speed. In addition, higher demands were now placed on the acceleration of trains, which gradually reduced them to lower services. After the First World War, nine examples came to France and were operated there by the État state railway as class 220.9. In the period that followed, the number of locomotives remaining in Germany decreased, which meant that the planned takeover of the last machines by the Reichsbahn and re-designation to the class 36⁷³ did not occur.

In view of the increasing loads in express train service around the turn of the century, the Grand Duchy of Baden State Railways launched a tender for a heavy express locomotive, in which seven designs took part. The requirement was to transport trains weighing 200 tonnes up gradients of 0.33 percent at a speed of 100 km/h. The contract went to Maffei, which also later developed the express trains for Baden.

In 1902, at the time of delivery, they were the largest of their kind in Europe with an operating weight of around 75 tonnes, which rested on a chassis with the axle configuration 4-4-2 (Atlantic). They were powered by a saturated compound engine, the four cylinders of which all acted on the first coupled axle. In contrast to the later Maffei express locomotives, the frame was not yet designed as a bar construction, but as a plate frame, as was usual at the time. Due to the elongated firebox, the distance between the rear coupled axle and the trailing axle was very large. The latter was designed as an Adam's axle, since the ash pan would not have allowed space for a drawbar.

Due to the long wheelbase and a large driving wheel diameter of 2,100 mm, the locomotives were remarkably smooth running right from the start. During test runs in 1904 with a train of four cars, top and average speeds of 144 and 116 km/h were reached. The first was broken three years later by the Bavarian S 2/6, which was also a Maffei design, but unlike the II d it was only developed as a one-off for test purposes.

The first production batch of twelve engines was manufactured by Maffei and delivered in 1902, another came in 1905 from the Karlsruhe mechanical engineering company and comprised six units. After the First World War, a total of ten engines had to be handed over to France. This left only seven units, as one engine had to be scrapped as early as 1903 due to an accident. The locomotives that remained in Germany were still intended to be redesignated as class 14⁴, but they could not expect a long life due to their only two coupled axles and were therefore retired in 1925. The now French locomotives remained in service for another nine years.

Since the locomotives from the early days were no longer powerful enough, newer ones with an 2-4-0 wheel arrangement were procured from Maffei in Munich. 20 of these were delivered from 1873 and were based on the Bavarian locomotives. It is noteworthy that from 1888 all of them were converted to tank locomotives with an 2-4-2T wheel arrangement and remained in use as such.

In order to increase the output, following the trend of the time, the grate area was enlarged without significantly increasing the dimensions of the boiler. A further increase in power was achieved through a higher boiler pressure, which had become possible due to new materials and production techniques. The locomotives had an external frame and external cylinders, but internal Stephenson-type valve gear. Braking, as was usual at the time, was done with mechanical transmission only to the wheels of the locomotive.

After a few years of operation, it became apparent that the adhesive weight was too low and the running characteristics with the long rear overhang were no longer up to date. Therefore, the locomotives were equipped with a trailing axle and turned into tank locomotives, while most parts remained the same. Because the weight of the boiler feed water was now acting on the couple axles, the adhesive weight increased. In addition, more powerful boilers of the Baden type were used later and the brakes were replaced with a modern air brake system of the Westinghouse type.

The conversion was completed on all locomotives in 1892 and extended their operating life beyond what the original tender locomotives would have achieved. The decommissioning began in 1901, the last locomotive was taken out of service in 1910.

The IV e was developed for passenger and express trains in order to supplement or replace the older, predominantly four-coupled locomotives in this role. It was all about the steep Black Forest Railway, where the existing locomotives could no longer cope with the increasing number of passengers. Thus, from 1894, Grafenstaden from Alsace supplied six-coupled engines with four-cylinder compound engines. They were the first locomotives with a 4-6-0 wheel arrangement in Germany, and they were also the first to use a de Glehn type engine on a locomotive with three coupled axles, i.e. with drive on two axles.

The running gear was built on an inside plate frame, while the bogie was designed with the outside frame known from Grafenstaden, despite the problematic running characteristics. The special feature of this engine rarely used in Germany was that the high-pressure cylinders were on the outside and the low-pressure cylinders on the inside, although the latter had a larger diameter. In order to achieve sufficient traction, the coupling wheels had a diameter of just 1,600 mm, which limited the speed to 90 km/h. During test runs, power of around 800 hp was measured and a 250-tonne train could be transported on the flat at 75 km/h.

Production comprised a total of 83 units up to 1901, which were also supplied by MBG Karlsruhe. Shortly after the turn of the century, the more powerful engines of classes II d and IV f pushed the IV e out of express service, and as a result it was only used in front of regular passenger trains. With the beginning of the First World War, decommissioning began, so that the Reichsbahn was able to take over 35 more units in 1925 and classify them as the class 38⁷⁰. The last were retired in 1932. Today, none of the locomotives remain, as the only existing one kept as a cutaway model in a museum burned down with the museum during World War II.

The IV f was an express locomotive with which the Munich company Maffei had won a competition held by the Grand Duchy of Baden State Railways in 1905. After three pre-series models built by Maffei, 32 more machines followed from the Karlsruhe mechanical engineering company. It was the first locomotive in Germany with the axle configuration 4-6-2, which is also known internationally under the American designation “Pacific”. The well-known Bavarian S 3/6 was later to become a development of the IV f.

The Pacific design and the bar frame instead of a plate frame were approaches that had been taken over from American locomotive construction. Nevertheless, the entire locomotive received a filigree and streamlined appearance, which was in contrast to the bulky American locomotives. In addition, the four-cylinder compound engine based on the Von Borries design was a typical feature of southern German express train locomotives.

Since the IV f was also to be used in mountainous areas away from the main Rhenish route, its 1,800 mm diameter coupled wheels were relatively small. As a result, a higher tractive force could be achieved on inclines than with larger wheels, but the entire engine reached high rotational speeds on flat land at high speeds, which also led to increased wear and consumption. To enlarge the grate area, the firebox was pulled behind the driving wheels and widened so that it is clearly visible from the outside. It was only because of this change and the resulting increased overhang that the 2'C wheel arrangement had to be abandoned and the trailing axle added. By balancing the load between the two rear axles, it was possible to increase the adhesive weight by around three tons on well-developed routes.

When it was taken over by the Reichsbahn in 1925, 22 of the 35 engines were still in use, which became the class 18². While the more numerous former S 3/6 remained in service for a long time despite the high-maintenance power plant, all examples of the former IV f were retired by 1930.

The Grand Duchy of Baden State Railways used the IV f from 1907 on its 413 km long main line from Mannheim to Constance. However, this was unable to cope with long, fast routes with its driving wheels, which were only 1,800 mm large. Thus, in 1915, the IV h was ordered from Maffei in Munich, where the IV f and the S 3/6 had already been manufactured. Since only use on flat routes was planned, the IV h received driving wheels with a diameter of 2,100 mm. This negatively affected acceleration, but made it possible to maintain high speeds for a long time. The certification was only for 110 km/h, which was 10 km/h faster than its predecessor series. It was only in the thirties that it proved on test drives at speeds of up to 155 km/h that it ran very smoothly even at higher speeds. It was therefore equipped with more powerful brakes and approved for 140 km/h.

The locomotive was powered by a four-cylinder compound engine, which combined characteristics of the De Glehn and Von Borries types. The low-pressure cylinders drove the second coupled wheel set and had to be located on the outside due to their large diameter. While the outer high-pressure cylinders on the De Glehn type were pulled back to achieve shorter connecting rods, the outer cylinders were at the height of the smoke chamber. Thus, the high-pressure cylinders were on the inside and drove the first set of coupled wheels. Since they were also pulled very far forward, they could be clearly seen from the outside.

When they were taken over by the Reichsbahn, they became the class 18³. After about ten years of service on the Baden trunk line, the 20 built IV h were replaced by class 01 standard locomotives and relocated to other locations. Although they had a higher fuel consumption than the newer locomotives, it later turned out that they could almost keep up with the 01 and even surpassed the 03 in terms of power. After all, the power measurements were in a range from 1,950 to 2,200 hp. 

After the war, all 19 remaining examples went to the Bundesbahn and only road number 18 314 ended up being traded for an S 3/6 to the Reichsbahn, where it was fundamentally rebuilt. All others were initially retired because their Number was very small. However, three were subsequently reactivated and modernized for use as brake locomotives or for other trials. The 18 316 was preserved and was again in running condition between 1995 and 2002, but was parked again after damage.