The American Locomotive Company (ALCO) model RS-3 is a 1,600-horsepower, B-B road switcher diesel-electric locomotive. It was manufactured by both ALCO in the United States and Montreal Locomotive Works (MLW) in Canada from May 1950 to August 1956. 1,418 were produced, 1,265 for American railroads and 98 for Canadian railroads. It has a single, 12 cylinder, model 244 diesel engine. Delaware Lackawanna 4103 is ex-Delaware & Hudson number 4103.