Giuseppe Zara of the Rete Adriatica (one of the two major railway companies in Italy at the beginning of the twentieth century); its design was very unorthodox, as the boiler was reversed on the frames, so that the cab and the firebox were leading and supported by the bogie, while the cylinders were at the rear.

[1] While simplifying the valve gear, this feature made it difficult to equalize the work done by each pair of cylinders, and this provoked hunting.

[1] As a result, the other forty-two were built by Ernesto Breda and the German firm Borsig-Werke.

Nicknamed Mucca (Italian for "cow"), the Class 670 spent its career on the mainline railways of the Po Valley; while quite fast and powerful for its day, the unorthodox shape of the locomotive in the end didn't prove successful, with more orthodox designs (like the FS Class 680) eventually being built.

Although it paved the way to other, more successful conversions, this locomotive was only meant as a trial essay, and was quickly discarded.