The 1970s C&O roster included the GP7 and the GP9, but no GP18's were present. AHM's GP18 is given C&O ownership and roadnumber 4301. The B&O had a single GP18m carrying roadnumber 6599. Information I've found shows it was traded in on GP40-2's in 1978 and was still wearing B&O blue when it left the roster. So, no GP18's prototypically wore Chessie System colors. B&O did own some GP9 Phase III diesels, which resemble the AHM GP18, however the B&O geeps had dynamic brakes.