It had been shown during the First World War that, from a servicing and maintenance point of view, it was a great disadvantage for each state railway to have its own locomotive classes with no standardization.

In addition, the military railways needed a fast, powerful, goods locomotive that did not have a high axle load.

The G 12 was the first locomotive commonly in service with multiple German state railways and thus rightly carries the name Einheitslokomotive, apart from "Kunibald" Wagner continuing the tradition of Garbe, and, later, handing the torch over to Friedrich Witte of the DB and Max Baumberg of the Deutsche Reichsbahn (DB).

In the 1920s, continuing well-constructed types (like the Bavarian S 3/6, Saxon XX HV, Prussian P 8 and others, including G 82 and G 12), came under serious consideration.

Wagner prevailed by stating that none of those machines offered the crucial standardisation of parts needed for economic operation.

Instead, the Einheitslok-1925 was a complete redesign, its genesis being described in detail by Alfred Gottwaldt, Geschichte der deutschen Einheits-Lokomotiven Franckh, Stuttgart 1978, ISBN 3-440-07941-4.

In addition, Baden bought 10 locomotives from the Prussian state railways.

Even the Deutsche Reichsbahn received a batch of 20 locomotives in 1924 that, following the Saxon XIII H, were given the numbers 58 443-462.

After World War II, locomotives 58 1669, 1746, 1767, 1904, 1917, 2122 and 2132 remained in Austrian national territory.

], two former Baden locomotives of the older type, 58 261 (Bw Chemnitz-Hilbersdorf) and 58 311 (Ettlingen), a Prussian original, 58 1616 (formerly used as a steam generator (Dampfspender) (Bw Hermeskeil) and an example obtained by Yugoslavia after WW2, 36-013, notably with the rear steam dome removed (Železniški Muzej Ljubljana), remain preserved.