They were built by the Belgian railway rolling stock manufacturer La Brugeoise et Nivelles between 1911 and 1919 for the Anglo-Argentine Tramways Company's (Compañía de Tranvías Anglo-Argentina (CTAA) in Spanish) first underground line.

They became the oldest underground rolling stock in commercial service in the world [1] as well as a tourist attraction and part of Buenos Aires cultural heritage.

Its loose end was fitted with the dead man's switch, a button-shaped mechanism that allowed the motorman to either enable or cut current flow to the motors in normal conditions.

Because of their long life-span, La Brugeoise trains used custom-made brake shoes made of hard wood embedded with creosote for additional resistance.

Friction between the steel wheels and the brake shoes released a peculiar fragrance that Line A became known for among porteños (as Buenos Aires inhabitants call themselves) and tourists.

If emergency brakes were engaged for more than 10 seconds, current flow to the traction motors and the auxiliary equipment was interrupted by the main fuse.

The interior was entirely made of finely carved wood, lit with 38 solid bronze globes using incandescent light bulbs.

On both sides of each sliding door, a seat was placed longitudinally to allow extra room for standing passengers to travel comfortably.

On 31 December 1926, the CTAA cancelled the mixed "tramway-metro" service as growing surface traffic caused delays to trains travelling through Rivadavia avenue.

Units 124 and 125 were newly manufactured at the Polvorín workshop in 1944 to enhance Subte services during World War II as a lack of imported spare parts for tramways and buses left most of the surface transport out of order.

Despite their 100 years of uninterrupted service, La Brugeoise trains had one of the lowest mechanical failure averages in the network: 19 every 100,000 km.

[4] Transport authorities replaced the cars with new rolling stock as soon as Line A reaches its new terminus, San Pedrito station.

In January 2010, national transport authorities announced that an agreement for the provision of 279 cars had been reached with Chinese rolling stock manufacturer CITIC.