Type A rotary cam poppet valve gear when she was already under construction, but such proposal was rejected due to technical difficulties in 1938., this decision unexpectedly prevented a lot of troubles that would have been caused by the problematic Franklin poppet valve gears in the T1's service life. The total service years or total service mileage of the S1 (from Nov 1939 to March 1940, Dec 1940 to May 1946) was ironically slightly longer than some of her younger duplex sisters. A time-book belonging to Pennsy engineman Byron Breininger from the Ft. Wayne division records a trip to Chicago on No. 6100 at 8:59 AM on May 5, 1946. This run was possibly one of its last in service, as less than two years later PRR president Martin W. Clement announced that “by May of this year (1948) we expect all of our through passenger trains west of the electrified territory to be dieselized”. Preservation of the S1 was discussed inside PRR's board, but due to the deteriorating financial situation since 1946, 6100 was scrapped in 1949. The PRR continued developing the T1 class of 4-4-4-4 duplex locomotives but wheel slip and mechanical failures also plagued the T1. Before Pennsylvania Railroad commissioned Baldwin for a 4-4-4-4 duplex passenger engine (T1) in 1940, Baldwin Locomotive Works already begun the development of designs for fast locomotives with duplex drive since 1938, including a rigid-frame 4-2-2-4 and three-cylinder 4-4-4 for lightweight trains and the preliminary design for a 4-4-4-4 for heavy trains; BLW presented these designs to several railroads, but only the PRR adopted the duplex concept. In Oct 1939, when PRR S1 was still on display in the 1939-40 World's Fair, Baldwin Locomotive Works placed a stock order to build a 4-4-4-4 duplex high-speed passenger locomotive as a demonstrator, with bullet nose streamlining by noted industrial designer Otto Kuhler, but before it could be built, the PRR placed an order for two locomotives of this type in July 1940. This implied that the PRR S1 was a showpiece exclusively built for the World's Fair instead of replacing the K4s as the new prime power of the PRR. The PRR T1 was developed at the same time when the S1 was under construction or on display in the World Fair. Cultural references The stylish appearance of the S1 has proved to be very popular: The S1 was represented in a 1939 painting