In the aftermath of the Spanish Civil War, Ferrocarriles Vascongados experienced a surge in passenger and freight traffic.

The three new locomotives were mechanically very similar to the older ones, but featured a more modern exterior design.

[4] After the original operator was absorbed into FEVE in 1972, the locomotives were renumbered as 4201 to 4203.

As part of the refurbishment, their exterior was reformed, they were fitted with Alliance couplers and their cabins were made similar to the ones used by 200 series trains.

[citation needed] The locomotives were named after mountains of the Basque Country.