Powered by a V12 FDL prime mover, the 2250 h.p. U23B was GE?s intermediate-sized four-axle road-switcher of the late 1960s through the mid 1970s. The U23B?s direct competitor during this period was the very successful EMD GP38. In 10 years of production from 1968 through 1977 a total of 481 units were produced, making this the second best seller of GE?s ?Universal Series? locomotives. The first units were delivered to the Delaware & Hudson in August and September 1968. CSX predecessors Chesapeake & Ohio and Louisville & Nashville had a combined fleet of 120 units, giving CSX one of the larger active fleets in later years. Penn Central, Santa Fe and Missouri Pacific also purchased sizeable fleets of U23Bs. Primary spotting features include a stepped-out radiator section and two sets of three tall engine access doors near the center of the long hood. During production, the U23B was equipped with various truck side frames, including Blomberg trucks from EMD trade-in locomotives, AAR-style trucks, or GE?s own four-axle ?FB2? truck. One of these three truck styles is included on our model where appropriate per road name. Today the number of active U23Bs has dwindled, but a handful can still be found working for short lines and regional railroads in North America.