Early Electro-Motive Corporation switchers were built with Winton 201-A engines. A total of 175 were built between February 1935 and January 1939. Two main series of locomotives were built, distinguished by engine size and output: the straight-8, 'S' series, and the V12, 'N' series. Both were offered with either one-piece cast underframes from General Steel Castings of Granite City, Illinois, denoted by 'C' after the power identifier, and fabricated, welded underframes built by EMC themselves, denoted by 'W'. This gave four model series: SC, SW, NC and NW. Further developments of the models gave model numbers NC1, NC2, NW1, and NW1A, all of which were practically indistinguishable externally from the others, as well as a pair of unique NW4 models for the Missouri Pacific Railroad and a solitary, twin-engined T transfer locomotive model built for the Illinois Central Railroad. S series The production S series locomotives are identical except for cast or welded underframes, which are identical to those used under the N-series locomotives. The hood on the S series is shorter, and the locomotives have a characteristic, rounded-edged "satchel" in front of the radiator. The straight-8 Winton 201-A engine moved the exhaust stacks off-center to the engineer's left, while the N series' were central. The Winton-engined switchers can be distinguished from later EMD 567-engined units by small louvres at the top front sides of their hoods, as well as top-of-hood ventilation through several lifting vents rather than the large top grille of those later units. The series was much more successful than the during this early period; 114 were sold. Pre-SC Two pre-production units were built in February 1935; they differed from full production units by having a hood that did not taper in toward the cab, and six rather than three small louvres on each top front hood side. They were delivered to the Delaware, Lackawanna and Western Railroad as 425 and 426. Both were re-engined with EMD 567 engines in 1962. One, 426, was purchased by the Delaware-Lackawanna Railroad and is on display at Steamtown National Historic Site in Lackawanna colors. SC 43 cast-frame SC units were built between May 1936 and January 1939. They were delivered to a wide assortment of railroads: Atchison, Topeka and Santa Fe Railway: 4 locomotives, #2301, 2151–2153 Inland Steel: 3 locomotives, #40, 42 & 44 New York Central Railroad: 7 locomotives, #567-573 (CR&I) Boston and Maine Railroad: 6 locomotives, #1103-1108 Chicago