The first engine of this type was developed by Karl Otto Keller in 1912.

The very few engines of this type produced were installed in Z-102 cars.

In all the Bavarian state railways procured 83 engines of this type over that period.

The first engine of this type built by the Cail company in 1868 was a 0-4-0+0-4-0 named "the Future".

Since an engine of this type does not exist, I, of necessity, had to invent one myself.

The Deutsche Reichsbahn took all engines of this type over.

To that end 470 engines of this type were procured between 1903 and 1910.

Kitson & Co. made many engines of this type.

Three engines of this type were built, all three of which have been preserved.

Only six engines of this type were ordered and produced.