I only knew the folio on a big unwieldy register where they entered all the details. That they are called bid ledger is news to me.
And I missed to mention one more thing. The tickets were like small card board rectangles similar to the ones coming out of the Weighing Machines these days. They also issued separate tickets for basic journey, reservation charges on the back of which the coach and berth number would be written, and super-fast charges. If you were travelling with a family of 4 you would have to keep 12 of these tickets.