In order to obtain a more powerful express locomotive than those with the 4-6-0 wheel arrangement, the Reichseisenbahnen in Alsace-Lorraine had some of the first Pacifics built in Europe in 1908. However, in order to be able to use existing turntables and at the same time allow a large tender, the trailing axle had a very small distance from the third driving axle. 

This meant that the Belpaire firebox had to be moved between the driving wheels, so the G 12 was not one of the typical Pacifics with a wide firebox. Typical of French-influenced areas, they had four cylinders based on the de Glehn system. Other features included serve tubes in the boiler and an exhaust system with a variable cross-section and cloverleaf shape.

Since the boiler and firebox were too small compared to other Pacifics and ten-wheelers, only eight S 12 were built. The seven that remained after the First World War came to SNCF in 1938 as 1-231 A. After the Second World War, three came to Luxembourg, two to the GDR and two to Poland. While they were used in Luxembourg until 1950 and in the GDR until 1953, the two in Poland were decommissioned in 1946 without actually being used.

Between 1900 and 1907, the Reichseisenbahnen Alsace-Lorraine procured a total of 215 tender locomotives based on the Prussian G 5². They also had a two-cylinder compound engine. In contrast, they were not only confined to freight trains, but also passenger trains if necessary, for which they received a continuous Westinghouse brake.

A total of four slightly different variants were built by a variety of manufacturers, the first three of which were designated the C29, C31 and C32. On the C32, the boiler was placed higher to make room for a deeper firebox. The last 71 locomotives received no special designation.

The low axle load ensured that the locomotives could be used freely. On branch lines in particular, they replaced old freight locomotives with a 0-6-0 wheel arrangement. Despite the low top speed, they were also actually used to pull passenger trains.

After the First World War, some locomotives were treated exactly like Prussian G 5², partly distributed to Germany and also taken to Poland and Lithuania. Those that remained in France were used by the SNCF from 1938 as 1-130 C until the 1950s. Seven were rescued to Luxembourg during World War II and became part of the CFL.

In order to be able to haul heavy passenger trains with a maximum axle load of 14 tonnes on branch lines, a tank locomotive with seven axles was required. Thus, the Reichseisenbahnen ordered a total of 66 locomotives from Grafenstaden in several batches with the 4-6-4T wheel arrangement and de Glehn four-cylinder compound engine. Although the locomotives briefly delivered almost 1,000 hp, they quickly reached their limits due to the low adhesive weight. After the Second World War, most of these locomotives were in Germany. Most of these came back to the SNCF and were retired by 1954. The Luxembourg CFL had also received some in the meantime.

In type I, the Grand Duchy of Mecklenburg Friedrich-Franz-Eisenbahn combined a total of six locomotives with a 2-2-2 wheel arrangement, which were primarily used to pull passenger trains. Among them was the “Marschall Vorwärts”, which had been named after Field Marshal Blücher. It was the first machine to be used on the Hagenow - Schwerin - Wismar line by what was then still known as the Mecklenburg Railway Company. It connected to the Berlin-Hamburg line that had just been opened by Prussia.

Although the first example was built as early as 1848, the design of the locomotives was already based on aspects that were more frequently encountered in later locomotives. These included, above all, an inside forked frame and cylinders mounted horizontally on the outside. The valve gear was arranged inside and designed according to the Stephenson design.

Since the procurement period stretched over 15 years, some machines differed from the others. Thus, the cylinders of the fourth and fifth machines were attached inclined to the smoke box. The sixth and last saw the boiler expanded from two to three shots and the firebox extended backwards over the trailing axle to provide a larger grate area. 

Although they only had a single driven axle, the locomotives were able to last a long time. This is mainly due to the fact that the Mecklenburg network was in flat country and the train weights remained relatively low due to the low population density. The first two machines were retired in 1890 and 1894, the rest followed in the years 1898 to 1901.

The Großherzoglich Mecklenburgische Friedrich-Franz-Eisenbahn ran steam locomotives for passenger and express trains under type III, which had been ordered from 1864 from the Sächsische Maschinenfabrik Hartmann in Chemnitz. They had become necessary because the classes I and II with a 2-2-2 wheel arrangement no longer had sufficient traction, especially on the newly opened lines in Mecklenburg Switzerland.

The general trend at the time was followed, to replace the rear carrying axle with a second coupled axle, resulting in the 2-4-0 wheel arrangement. The locomotives had an inner frame and outside cylinders with valve gear and valve bodies on the inside of the frame. A striking feature was the large steam dome, which was the same height as the chimney. In addition, there was no single sandbox on the boiler, but two smaller ones directly in front of the first dome axis.

In the years 1864, 1866 and 1869 Hartmann made a series, each of which had a higher boiler pressure than the previous series. This was initially 7.31 bars, then 8.04 bars and finally 8.77 bars, which in turn increased power. From the very first series, the locomotives had air brakes, which was not a matter of course at the time.

A total of 19 pieces were created, most of which were named after northern German cities. Only two pieces were given the names “Zwei Hundert” (Two Hundred) and “Vier Hundert” (Four Hundred) because of their special factory numbers. Their retirement began in 1901 and was completed in 1910.

The class XXI was one of the few locomotives that were specially procured for the Grand Duchy of Mecklenburg Friedrich-Franz-Eisenbahn. It arose from the fact that a tank locomotive like the Prussian T 9 was needed for branch lines, but the axle load was too high. Therefore, as the developer of the T 9, Henschel was commissioned to build a similar locomotive with an axle load of only twelve tonnes. The resulting XXI shared the same 2-6-0T axle formula and similar visual appearance, but was lighter and had smaller supplies. From 1910 it was given the designation T 4.

Between 1907 and 1922, Henschel and Orenstein & Koppel delivered 50 engines in slightly different designs to Mecklenburg, which became the class 91¹⁹ at the Reichsbahn. In addition, there were six more in 1919 and 1920 for the light railways in the province of Saxony, which later became the class 91⁶⁴. Depending on the year of construction and design, the locomotives had axle loads of between 11.8 and 14 tonnes with different amounts of coal and water. The driving wheels were either 1,150 or 1,200 mm in diameter and allowed a top speed of 45 or 50 km/h. Despite the lighter construction compared to the T 9, the indicated power could remain at the same level due to advances in technology.

The Reichsbahn took over all 50 Mecklenburg machines and later also those of the private railways after they had been nationalized. After the war only four locomotives came to the Bundesbahn, where they were retired by 1950. Two more were in Poland and were used there as TKi 100. The remaining 32 were all left in the East Zone. Half of them had to be handed over to the Soviet Union as reparations, where they were given the designation TT. The remaining half was used by the Reichsbahn together with the former private railway locomotives and retired by 1970.

Most of the locomotives of the Grand Duchy of Oldenburg Railway were based on a Prussian model. However, there was a problem when choosing a modern and powerful express locomotive, as the average axle load in the Oldenburg network was limited to just 15 tonnes. So they developed the S 10 with the 2-6-2 wheel arrangement, which is rare in Germany, on their own and had three pieces built by Hanomag.

It was the first superheated steam locomotive in Oldenburg, and the Lentz design valve gear was also used, which had already been used several times in Oldenburg. This consisted of four vertical valves per cylinder, which were actuated by a camshaft. Although it was not able to establish itself on other railroad companies, it did have some advantages over conventional slide valves. Efforts were also made to make maintenance easier in other places. Therefore, a two-cylinder engine with simple steam expansion was used and instead of complicated steering bogies, both carrying axles were designed as Adams axles.

Due to the overhanging firebox behind the coupled axles, the trailing axle had to be moved further back in order to achieve a balanced load distribution. In operation, however, it was noticed after a short time that this construction led to poor running characteristics, especially at high speeds. It was also found that the ratio of direct to tube heating surface was unfavorable. The resulting stresses caused leaks between the pipe wall and the pipes. Attempts were made to remedy this by using a copper firebox instead of steel, but this was not entirely successful.

After the founding of the Reichsbahn, the three locomotives were taken over as numbers 16 001 to 16 003. The class 16 came about because they were the only express locomotives with the wheel arrangement 2-6-2. Due to the shortcomings and the small number, however, they were retired in 1926 when they were less than ten years old. They were replaced by the Prussian P 8, which reached the same speed and had roughly the same power.

The G 1 was the first locomotive built directly for the Grand Ducal Oldenburg State Railways. Despite the “G” in the designation, they were designed as a universal locomotives for all train types. Also worth mentioning is the fact that the first engine “Landwuehrden” was also the first engine manufactured by the Munich locomotive manufacturer Krauss. This locomotive took part in the world exhibition in Paris in 1867 and was awarded a gold medal there.

The locomotives had two coupled axles and no carrying axles. With a diameter of 1,500 mm, the coupled wheels were large enough to also be used in front of passenger trains. There are different statements in the literature regarding the speeds that could be achieved, ranging from 45 to 50 to 60 km/h. In order to be able to use the engines without a tender depending on the occasion, the frame was designed as a water box. Thus, if the fuel was carried in the cab, shorter distances could also be covered as a tank locomotive. 

Up until around 1875, only peat was used as the fuel for all locomotives in Oldenburg in order to make the company independent of importing hard coal from outside its own country. Due to the lower calorific value of the peat, about twice the amount of fuel was required, which made it necessary to design the tender differently. As with the locomotive itself, the frame in the tender was used as a water tank in order to get more space for the peat in the body. In addition, the walls were about the same height as the cab. To protect the fuel from rain, there was a roof that had hatches for filling. The capacity of the tenders was around 3.5 to 4 cubic meters of water and 4.3 tonnes of peat. After the conversion to coal firing in the late 1870s, the tender's body was made lower. Some locomotives received completely new tenders with 10 cubic meters of water.

From around 1900, the engines were phased out, since more powerful ones were already available. The first example was taken to the German Museum in Munich with a mileage of 860,000 km due to its importance. The rest were decommissioned by 1925, so that the planned re-numbering of 19 of the 46 engines originally built as class 51⁷⁰ did not occur.