Studies were led in parallel with those of the 140 C. The 42-000s were of simple expansion with two cylinders and possessed the powerful fireboxes of the 140-100s.

Although the fireboxes were excellent, the rest was of average quality with cylinders particularly of small diameter (250 mm or 9.8 in).

The railway company was very satisfied with the engines as they were capable of hauling the heavy steel coaches.

This series of 20 engines, numbered 42-001 to 42-020, was built by Fives-Lille and was allocated to the Batignolles motive power depot.

The driver could operate the engine from the driving cabin of a Voiture État à 2 étages carriage at the other end of the train, using compressed-air pipes.