ILW’s rsx51/630 was that manufacturer’s first entry into the high(ish) horsepower 6-axle locomotive market. At 3000 HP these units were direct competitors against EMD’s SD40-2 model, so they did not get much traction at all in the market, only selling about 100 of them between 1988 and 1992, when they were dropped from the catalog due to not even having a hope to meet new emissions standards.

The D&H purchased 4 of them; the intention was to buy 30 of them to replace existing EMD power, but then the Chicago & Northwestern started retiring their fleet of ex-N&W C-628s and the bulk of the order became a (much cheaper) remanufacture of those well-travelled centuries, making these units the only 51/630s purchased by the PV&T.

As of 2025, three of the four (the fourth was retired and placed in the Parsons Vale’s museum in St-Constant, Québec) are operating on LT&L and Ottawa Central rails.