medium-distance use in its electrified territory. In 1963, they became known as Silverliner I cars when their use was supplemented by the Silverliner II, which used an improved Pioneer III body. They were placed into Philadelphia-area commuter rail service on the PRR and Reading Company lines. Budd was contracted in 1966 by the PRR and the U.S. Department of Commerce's Office of High-Speed Ground Transportation (prior to the establishment of USDOT) to build the original Metroliner multiple unit cars for luxury high-speed service on the northeast corridor. The 50 original cars were delivered in 1967–69. An additional 11 coaches were built for SEPTA but were not put into service until 1972 by Amtrak. The Metroliners have been either retired, rebuilt into coaches without the cabs, or de-powered and used as cab cars. The Silverliner II had a top speed of but ran at up to when the PRR used them its Philadelphia-Harrisburg service. The Metroliner EMU cars operated at 110 to but every car was tested to at least , although breakdowns in the system led Amtrak to derate them to . Since their retirement from regular service, Amtrak has used them as cab-coaches. Subway cars In 1960, Budd manufactured the first stainless steel production subway cars for Philadelphia's Market-Frankford Line. 270 M-3 cars were jointly owned by the City of Philadelphia and the Philadelphia Transportation Company (now Southeastern Pennsylvania Transportation Authority). Some rail enthusiasts nicknamed the cars "Almond Joys" because the four hump-shaped ventilators on the roof evoked the candy bar's shape. There were 46 single units and 112 "married" pairs. The pairs were a "mixed marriage" because the odd-numbered car came with General Electric motors and equipment and was permanently coupled to the even-numbered car, which had Westinghouse motors and equipment. Two cars in this fleet were air conditioned. These cars were replaced with more modern, air-conditioned M-4 units from 1997 to 1999. Some cars were transferred to the Norristown High Speed Line in the early 1990s. The cars had to be re-trucked, because the Norristown line is standard gauge (4' 8½") while the Market-Frankford line is Pennsylvania trolley gauge (5' 2½"). Industrial historian Jonathan Feldman has concluded that Budd, along with other "old-line" suppliers of subway cars, "lacked advanced systems-integration know-how and the skills required to manage complex electrical systems and electronics. Each of these firms had built railroad and subway cars, but modern subway cars became