In the early 1950s, the Comboios de Portugal saw the need to quickly convert the existing steam locomotives to other types of propulsion due to the lack of coal. The series 0300 railcars, of which 25 were built in 1954 and 1955, played a role in the changeover. They came from the Royal Dutch Factory for Furniture and Railway Vehicles Allan in Rotterdam, which earned them the nicknames “Allan” and “Holandesa”. The vehicles were equipped with two British AEC diesel engines, each delivering 220 hp, which transmitted their power to all four axles diesel-electrically.

The railcars had two cabs and could be used alone or in double. Per vehicle there were 24 first class seats, 50 second class seats and up to 34 standing places. There were no control cars, but one or two trailers could be coupled between two railcars. The vehicles were widely used and were equipped with new engines from the French company Poyaud in 1981 and 1982. 21 examples were converted to the series 0350 in 2000.