In 1935, the Reichsbahn procured two electric railcars with particularly generous glazing and initially referred to them as elT 1998 and elT 1999. They were built to show passengers the area on public or private special trips and, if necessary, also to increase the attractiveness of the railway in general as it faced increasing competition from road and air transport. In the new scheme from 1940 they became the ET 91.

Many measures were taken during construction to create the best possible view. The car body was glazed as generously as possible on the window fronts and also in the roof area without impairing its strength. The driver's cabs on both sides were located within the passenger compartment without any special separation and could only be separated from this with curtains for journeys at night with interior lighting. Furthermore, the partition walls between the passenger compartment and the entrance area were made of glass in the upper area and the toilet was installed as low as possible so as not to obstruct the view. With the exception of the pantographs, all the electrical equipment was laid under the floor of the car. A bogie was driven by two nose-suspended motors with a total of 390 kW and enabled the railcar to initially reach a speed of 120 km/h. This was reduced to 110 km/h after the installation of a sprung mounting, but in favor of the acceleration.

The two vehicles were based in Munich and were mainly used for tours in the Alps, often also in Austria and Switzerland. ET 91 02 was destroyed in a bomb attack in 1943, after which ET 91 01 was brought to safety about 60 km outside of Munich. This was also used by the Bundesbahn for special trips, right up until the time of the DB AG. From 1968 it received the class designation 491. Despite the increasingly difficult maintenance, it was not parked in the 1990s either. However, its life in service ended in December 1995 when it was badly damaged in a collision with a regional train in Garmisch-Partenkirchen. Today it is in the Augsburg railway park in a non-operational condition. The restoration began in 2005, but was not completed due to the major damage.