The Keystone was a set of eight lightweight streamlined cars built by the Budd Company in 1956 for the Pennsylvania Railroad. The set comprised seven coaches seating a total of 574 passengers and a single head end power (HEP) generator car. The train was normally used in New York, New York, to Washington, D.C., service, making two round trips per day. The design was not a success and the cars were retired in 1968.