Penn Central EMD SD45 6147 and ALCo C636 6343 pair up to power a freight in July 1970. The transparency is by David V. Leonard, and the location is probably Indianapolis. Both units came into Penn Central from the Pennsylvania Railroad with the same numbers. 6147, PRR class EF36, was built in 1966 and 6343, PRR class AF36, in 1968. Though from two different builders, both were 3600-horsepower locomotives. The EMD unit became Conrail 6147 in 1976, and was retired sometime after 1981; the ALCo unit appears to have been retired before passing to Conrail.