The Pennsylvania Railroad operated 425 Pacific type locomotives of class K4s, all but 75 of which it constructed in its Juniata Shops at Altoona, Pennsylvania. Like most of the railroad's steam locomotives they were numbered randomly with only a few large blocks of sequential numbers; thus their numbering ranged from 8 to 8378. Carl Weber provided this view of K4 No. 518 an ananymous photographer snapped at Bay Head, New Jersey in the 1950s. After World War II the PRR upgraded many of the K4s; Mr. Weber comments, "She has the full 'modernization' package of mechanical lubricator, stoker, and front end, with the solid pilot, smaller headlight in reverse position with the turbo-generator, and the 'maintenance/inspection veranda' mounted on the lower third of the smokebox front." No. 518 was one of 111 engines that rolled off the Juniata erecting floor in 1918.