Review for LEGO set 7815 Passenger Carriage / Sleeper from Brickset
Frist add-on for 7740 — “A good set to enhance your 7740 train. But it had a short selling period. As 7740 was replaced by 7745 in 1985, this one also disappeared. Lego did nothing similar for the high-speed train 7745, but the 9v Metroliner got an additional sleeper car in 1993.”
Full review at brickset.com