Describing the T42 as a “class” is possibly a bit excessive as there was just one of them (it)! However it had quite the legacy.
Built in 1953 by General Motors at their plant in La Grange, Illinois, this was intended as a demonstrator of their products for a European market at a time when much of the continent had brushed itself down after the end of the war and was preparing to oust steam. It was evaluated extensively around Europe, including in Sweden and Denmark, the Netherlands and Belgium, France, West Germany and Austria.
Much of this testing did lead to orders for GM, generally built under licence – the T41s in Sweden, the MYs in Denmark, the 52s, 53s and 54s in Belgium, the 2050s in Austria – and these too led on to further machines, such as the Hungarian M61s, Danish MXs, Swedish T43s and T44s and Norwegian Di3s from NoHAB and the Luxembourgish 1600s and then Belgian 55s and 62s from AFB and BN etc… It’s no exaggeration, therefore, to say that all of the “first wave” of General Motors diesels in mainland Western Europe can all be traced back to this one machine.
Above is a link to a video uploaded to YouTube by user Knut Ragnar Holme showing the T42 getting to grips with a heavy timber train.
The loco itself settled in Sweden in 1956 and was taken into SJ capital stock. It was withdrawn in 1983 and sold into preservation in Norway; it was repatriated to Sweden when it was sold to the Sveriges Järnvägsmuseum in 2007.
The T42 does have occasional outings on passenger trains; the only one currently in the diary is a trip with T41 204 to Rättvik on Thursday 2nd August 2018.