In 1970, Southern discontinued the Crescent through Montgomery while keeping the Southerner through Birmingham. Probably because the Crescent name had more prestige, it renamed the Southerner the Southern Crescent. This appeared to combine the names of the two trains but also could be read as the Southern [Railway] Crescent.
This brochure appears to have been given to passengers boarding the train in New York or other cities north of Washington. It notes that a full dining car and a club-lounge car would be added to the train in Washington, DC.