Complex sentence: After plans for a first-class passenger service were deemed to be unfeasible, the X2 and X3 quietly vanished; no evidence exists of their fate, but presumably, they were quietly broken up for scrap, probably around 1935.
Split into simpler sentences: After plans for a first-class passenger service were deemed to be unfeasible, the X2 and X3 quietly vanished. No evidence exists of their fate, but presumably, they were quietly broken up for scrap, probably around 1935.