As the first project in Italy to abandon the automobile-derived design and adopt a comprehensive "rolling stock" approach, it represents the link between the simple and sturdy Littorine and the modern Diesel units.

The increased passenger capacity, wider spaces and higher comfort levels were a good answer to all requirements specified by FS and a great progress compared to earlier models then in service.

Shunning the bigger companies like Fiat and Breda, FS ordered three prototypes of the new units to an experienced but smaller producer of parts and components based in Milan, Officine Meccaniche di Milano (OM).

The contract was quite challenging for OM, who until then had never managed to build a new line of rolling stock as the main contractor; that was the well-guarded fief of the two giants of the Italian heavy industry.

After a testing session along the Faentina railway line in Tuscany, the 772.1001 car was certified as compliant to FS specifications and brought into service; the first OM-built unit was delivered in November of the same year.

In 1939 the local railways Ferrovie Padane bought the three prototype cars from FS and two years later ordered from OM two additional units (FP ALn 72 1004-1005).

The outbreak of WWII reduced dramatically the request for passenger transport during the following years, except for large army convoys which were unsuited to the small Littorine; both Breda and OM converted their production to war effort.

OM could resume production only in 1948, thanks to the economic relief provided by the Marshall Plan and the huge efforts into bringing back the mangled national rail network to its pre-war standards.

In 1949 the SIF company, manager of the private railway Siena-Buonconvento-Monte Antico, ordered two additional cars to OM; unlike the FS units, which had a 4-number code, these were originally numbered 101 and 102.

Meanwhile, the fortunes of the series were not limited to the FS fleet, or to Italy alone: in 1949 three more special units were delivered to the Polish railways PKP, to be replicated and to serve on fast routes.

It was only years later, with age and the increased frequency of start-stop cycles required by the short-range services the units had been reassigned to, that the transmission gearing started to show heavy signs of wear and reliability problems.

The chassis, while similar in design to the earlier ALn 556, was one of the first in Italy to be electrically welded; the soundproofing was efficiently achieved thanks to the massive usage of asbestos fiber.

The twin BXD engines equipping the ALn 772 units were built by OM under license of the Swiss patent holder Adolph Saurer AG.

The bogies, in turn, not having to sustain the engines' weight, were redesigned by taking inspiration from those of the first electrical railway motor cars: they featured journal boxes on the external part of the frame, a main volute spring suspension and an auxiliary one based on the traditional leaf-spring design.

The main priority was rebuilding the Polish passenger service in short time: electrified lines were far too expensive, as were powerful steam locomotives, so the Diesel motor car technology was chosen as the cheapest and fastest to set up.

In the past PKP had already used some motor cars, mainly built by Hipolit Cegielski, in Poznań, by Fablok in Chorzów, or by Lilpop, Rau & Loewenstein in Warsaw.

They included a fleet of six fast cars called Luxtorpeda, with top speed of 120 km/h (75 mph), which operated from 1934 to 1939 between Warsaw, Katowice, Kraków, Zakopane and Poznań.

Being aware of this situation, Franciszek Tatara, then president of the agency controlling the Poznań vehicle factory, had the idea of buying some of the new Italian cars and paying them with good-quality coal.

The ALn 772 design was then used by OM to build a special group of three units, which were named SD80 and marked with codes 09051 to 09053, which were then transferred to Poland in 1949, through Austrian and Czech railways.