At the turn of the century, Enrico Plancher, chief engineer of the Rete Adriatica, was looking for a solution to accommodate large fireboxes while eliminating the obstruction of visibility from the smoke. His approach was to place a ten-wheeler in reverse and use it to pull the firebox forward. As a result, it had enough space above the bogie and could accommodate a large grate. Since the driver's cab was now also in the front, the view was no longer restricted by the smoke, which was a great advantage, especially when driving through tunnels.

Oblique rear view

Railway and Locomotive Engineering, August 1904

While the problem of firing in later cab-forward locomotives was solved with oil or coal dust, the coal in the Rete Adriatica locomotives had to be carried in the driver's cab, which made them semi-tank locomotives. Instead of a tender with water and coal, only a simple, three-axle tank car was carried. The compound engine was designed according to Plancher's own plans, with the two high-pressure cylinders on the right and the low-pressure cylinders on the left, and a total of only two Heusinger controls.

No. 6943 on an old postcard

Fernand Fleury

Initially, only two prototypes were made, the first of which was shown at the World Exhibition in Paris and was then loaned to the French Ouest for a month and a half on a trial basis. A total of 43 examples were built by 1906, some of which were built by Borsig in Germany. The last ones were already assigned to the FS at the factory and classified in Baureihe 670.

Although the positioning of the driver's cab was advantageous in theory, it revealed serious disadvantages in operation. Since the boiler was located behind the crew in the direction of travel, the boiler and the track could not be observed at the same time. Nevertheless, from 1919 the locomotives were equipped with new boilers with superheaters, which increased the output by 15 percent. These locomotives were listed as Baureihe 671 and were used until the early 1930s. As late as 1936, a locomotive was saved from being scrapped by being used as a test vehicle for the Franco Crosti feed water heater and designated Baureihe 672.

In order to modernize the locomotive park on the Sicilian network and to ensure the operation of passenger trains on new routes, Guglielmo Cappa developed the class H. Since the same maximum speed should be achieved in both directions and the locomotives should also be able to be used on secondary routes, it was designed as a tank locomotive with a 2-6-2T wheel arrangement and an axle load of 14 tonnes. It was powered by a two-cylinder compound engine with a high-pressure cylinder on the left side. In order to ensure sufficient traction on the mountainous routes in Sicily, the coupled wheels were designed with a diameter of just 1,510 mm.

The first six pieces were delivered to the Rete Sicula in 1905 and numbered 401 to 406. The next six have already been taken over directly by the FS and, together with the first ones, have been classified in the number range from 9101 to 9112. Since the good acceleration of the locomotives was also suitable for suburban traffic, another 42 units were ordered and stationed in Milan. The remaining machines soon came to Milan and were used there until 1955. Some engines had come to Yugoslavia during World War II and remained there after the war ended.

One example was experimentally converted into a diesel Zarlatti locomotive in 1929. The boiler was replaced with a two-stroke diesel with a compressor and connected compressed air tank. The engine filled the tank and the compressed air was eventually used to power the steam locomotive's original cylinders. Although this principle worked in general, it still had technical difficulties and was not pursued further.