the design flaws of the s1 led to only one example being produced. before s1 was officially put in revenue service, the prr already ordered a shorter design, the t1 4-4-4-4 t1 of 1942. unlike her duplexes sisters, prr s1 didn't install any poppet valve gear, even though it was proposed to install franklin 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 s1's service life. the total service years or total service mileage of s1 (from nov 1939 to march 1940, dec 1940 to may 1946) was ironically slightly longer than some of her younger duplex sisters.