At some point between 1972 and 1979, EAV ABe 4/4 71 was rebuilt into a BDe 4/4, increasing the number of such consists that the SOB could offer.
The pair of De 4/4 were also used for some trains. Service to Einsiedeln from Biberbrugg was often old generation ABe 4/4. There were however, not enough pilot coaches for use in all the trains.
We used to watch the trains run through Wollerau and up along Erlenstrasse on their way to Samstagern or back. Today, what was then fields are now built up and you can no longer see the train line from where we used to observe them from.