In 1953 ALCo. introduced the DL500 specification, the "World" locomotive intended for the export market, with the fielding of demonstrator unit #1953C, built in Canada's ALCO. subsidiary MLW. Four years later the Argentinean State Railroads responded with a 25 unit order, DL500C's model FPD7, which became the only diesels built under that specification by MLW besides the demo. Happy with the good response from the market, ALCo's 1956 Export Catalog introduced new model RSD16, specification DL540, which was basically the DL500 undera road-switcher carbody instead of the former cab-unit configuration. And once again Argentina came back with a new order, this time for 130 locomotives that ALCo's Schenectady Plant built between December 1957 and February 1959. One example of each model, RSD16 # 8502 and FPD7 #8402, paired in a Buenos Aires al Pacifico Railroad's westbound freight train leaving Alianza Yard as it entered the mainline in Caseros suburban station.