These are the old switchers but they look a lot the same to me. I know the C&O bought a couple sets of the TRs with cow and calf. Was thinking about trying to make a set using existing stuff.
wikipedia isn't faultless, but it seams they are NW-2s without cabs http://en.wikipedia.org/wiki/EMD_TR3 They are cow-calf-calf
I'll have to get out my Early Diesels spotting book as it has a very good lineage of the early EMD switchers and their heritage, including the cow-calf units. Will have you an answer tomorrow afternoon if someone else doesn't find it first.
here is a NW2... http://espee.railfan.net/nonindex/sw_photos/1937_sp-nw2-bob_dengler.jpg and a SW9... http://espee.railfan.net/nonindex/sw_photos/2207_ssw-sw9-ed_cooper.jpg
Sorry, got behind on stuff and didn't get around to the book. Anyway, here's what it says - NW2 Power: 1000HP, Engine: 567, 567A Number Produced: US: 1117 Canada: 24 Features: Two Centered Stacks, half-height radiator grille, no sandbox on the front platform. The lack of small screened openings along the top of the hood sides at the front differentiates the NW2 from its 201-A-engine predecessors. Has curved cab windows over hood. SW9 Power: 1200HP Engine: 567B Number Produced: US: 778 Canada: 30 Features: Has onlylower set of hoodside vents (NW2 & SW7 have upper and lower sets) and six louvers in the battery box behind the cab. Two centered stacks and full-height radiator grille. Has rectangular cab windows over the hood. SW1200 Power: 1200 HP Engine: 567C Number Produced: US: 737 Canada: 287 Features: Same as SW9 except 5 louvers on battery box instead of 6. Some SW1200's equipped with Flexicoil trucks for road service. Late-production Canadian SW1200's with Flexicoil trucks also have a large projecting number board and headlight assembly. TR3 Power: 3000 HP Engine: 567A Number Produced: US: 2 Canada: 0 Features: 2 two three-unit sets ("herds") built by EMD in 1949 for Chesapeak & Ohio using 1 NW2 and 2 cabless boosters connected by drawbars. Also, the C&O purchased 2 TR4's, which were an SW7 cow-and-calf pair. The SW7 was basically an NW2 with the 1200 HP 567A engine installed in place of the original 1000HP 567.
