The P5, P5a, P5am and P5b were Pennsylvania Railroad electrics, built between 1931 and 1935 in collaboration with GE and Baldwin-Westinghouse. The P5 was the prototype; two were made. It had a 2-C-2 wheel arrangement. http://www.davesrailpix.com/prr/htm/bvpr073.htm The P5a was the most numerous version. Note the large, boxy structure above one of the trucks. http://www.davesrailpix.com/prr/htm/bvpr207.htm http://www.davesrailpix.com/prr/htm/bvpr142.htm http://www.davesrailpix.com/prr/htm/bvpr019.htm http://www.northeast.railfan.net/images/prr4727.jpg http://www.davesrailpix.com/prr/htm/bvpr208.htm The P5am cannot be mistaken for any of the others. It still has a 2-C-2 wheel arrangement, but it has the body styling of a GG1. http://www.rr-fallenflags.org/prr/prr4770.jpg http://www.northeast.railfan.net/images/tr_prr4780.jpg http://www.davesrailpix.com/prr/htm/bvpr167.htm The P5b was a modification of a P5a, with a B-C-B wheel arrangement. Note the extra grilles below the usual ones. http://www.davesrailpix.com/prr/htm/bvpr159.htm http://www.davesrailpix.com/prr/htm/bvpr160.htm http://www.davesrailpix.com/prr/htm/bvpr209.htm P5am leads a P5a http://www.davesrailpix.com/prr/htm/bvpr212.htm P5am leads a P5a http://www.davesrailpix.com/prr/htm/bvpr168.htm P5am leads a P5a http://www.prrths.com/Phila_Images/P5A@Sharon%20Hill-1944.JPG P5am leads a P5a http://www.davesrailpix.com/prr/htm/bvpr156.htm P5am leads two P5as http://www.davesrailpix.com/prr/htm/bvpr176.htm P5am leads two P5as http://www.davesrailpix.com/prr/htm/bvpr177.htm P5am leads two P5as http://www.davesrailpix.com/prr/htm/bvpr213.htm P5am leads three P5as http://www.davesrailpix.com/prr/htm/bvpr215.htm P5am leads a P5a, with a GG1 on the farther track It can be observed that P5ams tended to lead P5as, rather than the other way round. This was because of the poor collision safety of the boxcabs.