Chesapeake & Ohio owned the ONLY two TR3 sets ever made, #6500 and 6501. The TR3 was an A-B-B set (or cow-calf-calf, thus nicknamed 'the herd') of NW2's built by EMD. Each unit was rated 1000 HP, so the herd was rated 3000 HP. They were bought in May 1949 for hump switching (mostly coal hoppers) at C&O huge coal classification yard at Russell, KY. They were later broken up and sold to B&O, being renumbered 9552-9557. At least one unit (9557) received Chessie colors.