Such is the case with its T1 class 4-4-4-4 duplex locomotives. In spring 1942, prototypes Nos. 6110 and 6111 were quietly rolled from the Baldwin Locomotive Works. The Pennsy liked what they saw ...

Meanwhile, the Pennsylvania Railroad went the "duplex" route, taking the hinge out of the design and fixing two engine sets onto a rigid frame. The PRR manufactured 83 locomotives between 1937 and ...