I took this photo one morning in March of 2007.
Seen here Idling between switching chores, is a 1966 vintage EMD SW 1500 yard switcher with a slug motor near the yard office on west 63rd Street. The slug motor, does not have a diesel prime mover inside. The unit is a frame and trucks from an older retired / scrapped yard switcher. The electric motors in the trucks are powered via cables from the locomotive. The body above the frame is all steel and concrete for weight. While not fast, they are powerful for heavy yard switching and road transfers. Sometimes they can be found on switching locals.