Another experimental member of Pennsylvania Railroad's K4s class, No. 5399, poses in Chicago on December 14, 1947. She has the repositioned headlight and turbogenerator applied to many of the K4s class in later years, though not the solid steel pilot. Most notably, however, No. 5399 displays her Franklin type A oscillating cam poppet valves and front-end throttle, a conversion carried out by Lima Locomotive Works in 1939. According to Carl Weber, who supplied the image, this modification resulted in a 44% increase in drawbar horsepower at 80 miles per hour, an advantage that influenced the PRR to apply this type of valve gear to the T1 duplex drive in place of the more conventional Walschaerts motion. No. 5399's side skirting also anticipates the T1 styling. No. 5371 rolled off the Altoona erecting floor in 1924.