This model was a fairly short-lived offering from Bachmann (released circa 1976 and discontinued circa 1981). AFAIK, it was only available in auto-train livery (catalog #5650). Although sold separately, it was most noteably included as part of Bachmann's auto-train trainset -
Although the U36B and dome-coach models lived on for decades, the auto transporter was (for whatever reason) dropped relatively quickly.