This detailed Atlas HO Scale Master Silver Alco S4 is modeled after diesels built by the American Locomotive Company between 1949 and 1957. The 1,000-horsepower diesel-electric switchers were designed to replace older steam switchers. Almost 800 S4s featured a six cylinder 539 prime mover and rode on AAR Type A Trucks (which distinguished them from nearly identical S2s). Whether operated by their original owners or secondary owners, several of these venerable workhorses are still working in the 2020s and others are preserved in museums or on excursion railroads. This Atlas model features a five-pole, skew-wound motor with dual flywheels, directional LED lighting, Accumate(R) magnetic knuckle couplers, accurate decoration and roadname-appropriate body details. This sound-ready diesel comes equipped with a 21-pin DCC socket and factory-installed speaker for easy decoder installation when you're ready.